Approximately two-thirds of states have functional parent doctrines, which enable courts to extend parental rights based on the conduct of forming a parental relationship with a child. Different jurisdictions use different names—including de facto parentage, in loco parentis, psychological parenthood, or presumed parentage—and the doctrines arise from different sources of authority—common law, equitable, and statutory. While much has been written about functional parent doctrines, relatively little is known about how they work in practice.

This Article fills that gap by documenting how functional parent doctrines operate, examining when, how, and to whom courts apply them. We collected and coded every electronically available functional parent decision issued between 1980 and 2021—669 cases in all—from every jurisdiction that has a functional parent doctrine.

Our study reveals that common assumptions about functional parent doctrines fail to reflect the contexts in which such claims arise, the individuals who assert such claims, and the roles that the parties played in the children’s lives. Among cases in our data set, relatives, and grandparents in particular, constitute a large share of the functional parents. In the overwhelming majority of cases, the functional parent has been the child’s primary caregiver. And courts routinely apply functional parent doctrines to protect children’s relationships with the person who is parenting them. In sum, we find that courts commonly apply the doctrines in ways that make children’s lives more stable and secure by protecting their relationships with their primary caregivers and preserving their home placements.

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Ronda and her newborn daughter, Brittanae, lived with Ronetta, Ronda’s mother and Brittanae’s grandmother, until Ronda died when Brittanae was nineteen months old. 1 State ex rel. Combs v. O’Neal, 662 N.W.2d 231, 233–34 (Neb. Ct. App. 2003). After her mother’s death, Brittanae remained with her grandmother. 2 Id. Almost a decade later, Brittanae’s father, Adrian, sought custody of her. 3 Id. Adrian testified that during that decade, he had contacted Brittanae by phone or in person at least monthly. 4 Id. at 234. At the time of trial, Brittanae was thirteen. 5 Id. She testified that she lived with Ronetta, whom she called “mom” her  entire  life,  and  wanted  to  remain  with  her. 6 Id. Indeed, she testified that “it would be extremely stressful or unbearable to move in with Adrian.” 7 Id. at 235. The trial court found that Ronetta stood in loco parentis—“a person who has fully put himself or herself in the situation of a lawful parent by assuming all the obligations incident to the parental relationship and who actually discharges those obligations.” 8 Id. at 236–37. Having reached that conclusion, the Nebraska courts further determined that “Ronetta’s continued  custody  is  clearly  in  Brittanae’s  best  interests.” 9 Id. at 237.

Karina had a child with Jose. 10 In re Custody of S.A.-M., 489 P.3d 259, 261 (Wash. Ct. App. 2021). When the child was eighteen months old, Karina began living with Gabriel. 11 Id. Around that time, Jose moved halfway across the country. 12 See id. (noting that Jose moved to Oklahoma from Washington, where Karina remained). After moving, Jose was “largely absent” from the child’s life. 13 Id. at 262. “[A]lthough he engaged in periodic phone calls every three to four months,” he visited the child only once during the four years from 2012 to 2016. 14 Id. During this same period, Karina and Gabriel lived together as a family. Gabriel was the “only father [the child] knew”; the child considered Gabriel her father and called him “dad.” 15 Id. Karina and Gabriel became engaged, but, before they could marry, Karina was murdered. 16 Id. The child was five at the time. 17 See id. at 261. Both Gabriel and Jose sought custody. 18 Id. at 262. After the trial court began transitioning custody to Jose, the child’s “grades in school fell, and her mental health deteriorated.” 19 Id. Eventually, the Washington courts recognized Gabriel as the child’s de facto parent and awarded him primary custody. 20 Id. at 267.

When L.M. was born, his biological mother, who had a substance use disorder, asked another woman, M.W., to “take and raise” him. 21 See In re L.M., No. C072731, 2014 WL 5841572, at *1 (Cal. Ct. App. Nov. 12, 2014). The biological mother “had no contact with M.W. or [L.M.]” for several years. 22 Id. M.W. “was his sole caretaker, and provided for all his needs.” 23 Id. at *4. M.W. “enrolled [L.M.] in school and took him to medical appointments, representing herself as his mother.” 24 Id.  Teachers and the parents of other children “all knew M.W. as [L.M.’s] mother, as did the members of M.W.’s church.” 25 Id. When he was six, L.M. found out that M.W. was not his biological mother. This fact came to light when the state initiated abuse and neglect proceedings against his biological mother based in part on “the fact that [she] had not cared for the minor since his birth nor was she able to adequately do so.” 26 Id. at *3. The California courts recognized M.W. as L.M.’s presumed parent because she “held the minor out as her own.” 27 Id. at *4. As a result, L.M. was able to remain living with the person who had parented him his entire life, rather than being placed in the state’s custody. 28 Id. at *8 (noting that the state could not claim jurisdiction over L.M. since there were “no allegations . . . that the minor was at risk in M.W.’s care”).

In the first case, Nebraska’s functional parent doctrine—in loco parentis—allowed the court to recognize the parent–child bond that existed between Ronetta and Brittanae, despite their lack of a biological or adoptive parent–child relationship. 29 See State ex rel. Combs v. O’Neal, 662 N.W.2d 231, 234 (Neb. Ct. App. 2003). In the absence of this doctrine, Brittanae likely would have been removed from the only home she had ever known and placed with a man who had “not assume[d] the obligations incident to being a parent,” even though he “knew that he was Brittanae’s father.” 30 Id. at 237. The other route for protection—the state’s grandparent visitation statute—authorizes only an award of visitation, not custody. 31 See Neb. Rev. Stat. § 43-1802(1) (2016) (providing that “[a] grandparent may seek visitation with his or her minor grandchild if,” among other conditions, the child’s parents are deceased).

In the second case, Gabriel amended his original complaint to include a claim under Washington’s newly enacted de facto parent statute. 32 In re Custody of S.A.-M., 489 P.3d 259, 263 (Wash. Ct. App. 2021). Prior to the enactment of the statute, Washington applied a common law de facto parent doctrine. See Carvin v. Britain (In re Parentage of L.B.), 122 P.3d 161, 163 (Wash. 2005) (holding that “Washington’s common law recognizes the status of de facto parents”). Because, under Washington law, a de facto parent “stands in legal parity with an otherwise legal parent,” 33 In re Custody of S.A.-M., 489 P.3d at 265 (quoting In re Parentage of L.B., 122 P.3d at 177). the custody dispute turned on the child’s best interest. Accordingly, the court ruled based on the “strength, nature, and stability” of the parent–child relationship that existed in fact. 34 Id. at 266 (quoting Wash. Rev. Code Ann. § 26.09.187(3)(a) (West 2022)).

In the third case, California’s functional parent doctrine—a presumption of parentage based on “receiv[ing] the child into [one’s] home” and “hold[ing] the child out as [one’s] own”—allowed the court to avoid “tear[ing] from the minor the only parent he has ever known.” 35 In re L.M., No. C072731, 2014 WL 5841572, at *3, *6 (Cal. Ct. App. Nov. 12, 2014). In fact, if M.W.’s parentage petition had been denied, the state likely would have taken custody of L.M., given evidence demonstrating that the biological mother was unable to care for the child. 36 Id. at *8.

Today, approximately two-thirds of the states have a functional parent doctrine. 37 We identify thirty-four such jurisdictions. See infra Part II. Appendix A identifies the various functional parent doctrines in the jurisdictions we include. Different jurisdictions capture functional parenthood through different doctrines. These doctrines include ones scholars have long addressed—such as de facto parentage, psychological parenthood, in loco parentis, and the “holding out” presumption of parentage. 38 See infra Part II. They also in­clude doctrines that have received relatively little attention—such as de facto custodian and equitable caregiver statutes and a presumption based on “notoriously” recognizing parentage. 39 See infra Part II. These doctrines arise from dif­ferent sources of authority across jurisdictions—common law, equitable, and statutory. 40 See infra Part II. In some jurisdictions, like Nebraska, the doctrines are judicial creations; in others, like California, they are codified. 41 See infra Part II. And some states, like Washington, have multiple doctrines. 42 See infra Part II. These doctrines yield different rights and obligations across jurisdictions, with some granting full legal parentage and others extending only limited parental rights. 43 See infra notes 132–144 and accompanying text.

In recent years, functional parent doctrines—at least the more familiar types—have garnered significant attention from scholars, judges, lawmakers, advocates, and the media. 44 With regard to legal scholarship, a Westlaw search in “Law Reviews & Journals” for [“de facto parent!” & da(aft 01/01/2010)] turns up 588 articles as of February 26, 2023. A few of the hundreds of articles in this long list include the following: Libby Adler, Inconceivable: Status, Contract, and the Search for a Legal Basis for Gay & Lesbian Parenthood, 123 Penn St. L. Rev. 1 (2018); Katharine K. Baker, Quacking Like a Duck? Functional Parenthood Doctrine and Same-Sex Parents, 92 Chi.-Kent L. Rev. 135 (2017) [hereinafter Baker, Quacking]; Courtney Megan Cahill, Regulating at the Margins: Non-Traditional Kinship and the Legal Regulation of Intimate and Family Life, 54 Ariz. L. Rev. 43 (2012); William N. Eskridge Jr., Family Law Pluralism: The Guided-Choice Regime of Menus, Default Rules, and Override Rules, 100 Geo. L.J. 1881 (2012); Jessica Feinberg, Whither the Functional Parent? Revisiting Equitable Parenthood Doctrines in Light of Same-Sex Parents’ Increased Access to Obtaining Formal Legal Parent Status, 83 Brook. L. Rev. 55 (2017); Susan Hazeldean, Illegitimate Parents, 55 U.C. Davis L. Rev. 1583 (2022); Michael J. Higdon, The Quasi-Parent Conundrum, 90 U. Colo. L. Rev. 941 (2019); Clare Huntington & Elizabeth S. Scott, Conceptualizing Legal Childhood in the Twenty-First Century, 118 Mich. L. Rev. 1371 (2020); Pamela Laufer-Ukeles & Ayelet Blecher-Prigat, Between Function and Form: Towards a Differentiated Model of Functional Parenthood, 20 Geo. Mason L. Rev. 419 (2013); Gregg Strauss, What Role Remains for De Facto Parenthood?, 46 Fla. St. U. L. Rev. 909 (2019). Yet, cases like the ones from Nebraska, Washington, and California discussed above are rarely part of the conversation. Instead, commentary tends to make assumptions about how the doctrines operate without a solid empirical basis. 45 See infra Part IV. For all that is written about functional parent doctrines, relatively little is known about how these doctrines work in practice. In what kinds of cases do functional parent claims arise? Who are functional parents in these cases, and what is their relationship to the legal parents and to the child? What role do the functional parents serve in the child’s life? Answering these questions and others can provide important insights with which to evaluate, design, and refine functional parent doctrines.

This Article documents how functional parent doctrines operate in practice, examining when, how, and to whom they apply. It does so by providing an empirical account of functional parent case law. We have collected and coded all electronically available judicial decisions from 1980 to 2021 in every U.S. jurisdiction that has what we categorize as a functional parent doctrine. 46 We used Westlaw to collect cases. While we undertook some investigation to ensure that Westlaw and Lexis searches turned up the same cases, it could very well be that comprehensive searches of other databases, including Lexis, would produce additional decisions. At least with respect to federal appellate decisions, recent work has shown that for some federal courts of appeals, Lexis and Bloomberg contain more decisions than Westlaw, whereas for other federal courts of appeals, Westlaw contains more decisions than Lexis and Bloomberg. See Merritt E. McAlister, Missing Decisions, 169 U. Pa. L. Rev. 1101, 1126 (2021) (comparing the number of merits decisions self-reported by the twelve courts of appeals with the numbers of circuit court opinions found on Westlaw, Lexis, and Bloomberg). By this we mean a doctrine that extends parental rights to an individual based on the conduct of forming a parental relationship with the child and parenting the child. 47 In Part I, we describe the universe of functional parent doctrines and explain why we generally exclude third-party custody statutes and doctrines that turn on an individual’s status (e.g., a grandparent or stepparent). Our data set includes doctrines in thirty-two jurisdictions. Functional parent doctrines now exist in thirty-four jurisdictions, but the statutes in Georgia and Connecticut took effect in 2019 and 2022, respectively, and yielded no electronically available cases during the period we studied. 48 See Ga. Code Ann. § 19-7-3.1 (2022) (providing for “equitable caregiver” status and noting that statutory scheme was enacted in 2019); Pub. Act No. 21-15 (Conn. 2022), [].

In total, our data set includes 669 decisions. 49 As explained infra in Part II, all but twenty-eight decisions in our data set are appellate decisions. See infra note 178 and accompanying text. It includes cases decided under judicially created doctrines, like in loco parentis and psychological parenthood, as well as codified provisions, such  as  the  “holding  out”  presumption  and  de  facto  custodian. 50 See infra notes 78–95 and accompanying text. It includes doctrines that treat functional parents as legal parents, as well as those that grant functional parents only some parental rights, such as standing to seek custody. 51 See infra notes 183–187 and accompanying text. Some jurisdictions have more than one relevant doctrine. 52 See infra note 182 and accompanying text. Where this is the case, all of the relevant doctrines are included in the data set.

Although, like all empirical studies, our study has limitations, it nonetheless provides a clear-eyed and thorough assessment of functional parent doctrines and how they operate in litigation. In the overwhelming majority of cases in the data set, the functional parent appears to have been the child’s primary caregiver. 53 We use the term “functional parent” to include all claimants under functional parent doctrines, even though the status of the person as a functional parent is what the court is being asked to determine. In other words, “functional parent” as used in this Article’s discussion of the empirical study includes persons alleged to be functional parents in these cases, even if the court ultimately determines that the person does not meet the legal standard to be a functional parent. In many cases in our study, the functional parent is the only person who has consistently cared for the child. 54 See infra section III.B; see also Courtney G. Joslin & Douglas NeJaime, Multi-Parent Families: Real and Imagined, 90 Fordham L. Rev. 2561, 2579–85 (2022) (describing such cases based on our West Virginia data set) [hereinafter Joslin & NeJaime, Multi-Parent Families]. Seeking to avoid disruption of this parent–child relationship, courts in our study routinely apply functional parent doctrines to protect children’s relationships with the person who is in fact parenting them.

The account this Article offers looks different than the picture pre­sented in contemporary commentary. 55 See infra Part IV. Scholars and advocates typically assume a paradigmatic claimant in functional parenthood cases: the nonbiological parent in a same-sex couple. On this view, the doctrines’ primary beneficiaries are LGBTQ parents who had been excluded from protections under discriminatory parentage rules. 56 See, e.g., Baker, Quacking, supra note 44, at 135 (describing “[t]he typical functional parent doctrine claim in the same-sex parent context”). Commentators also typically imagine a paradigmatic context—post-dissolution custody disputes—in which functional parent claims arise. 57 See, e.g., id. at 165–68 (discussing “[c]ontested custody disputes” to critique functional parent doctrines and asserting that “[h]igh conflict legal disputes between parents are notoriously bad for children”). In this vision, the doctrines primarily arise when a former intimate partner who had cared for the child alongside the legal parent seeks custody or visitation over the legal parent’s objection. 58 See Brian Bix, Against Functional Approaches, Jotwell (Jan. 12, 2022), [] (“[O]ften one member of a couple is resisting the claim . . . , and the resisting partner will not want the claim recognized and will almost certainly not want the intrusiveness of the inquiry.” (emphasis omitted)). It is assumed that, but for the functional parent’s claim, the state would otherwise not be involved in the lives of the legal parent or child. 59 See Laufer-Ukeles & Blecher-Prigat, supra note 44, at 461 (writing supportively of functional doctrines while observing that “functional parenthood makes formal parents uneasy about state interference with the parent–child relationship”). Because bitter custody disputes are not good for chil­dren, scholars and advocates worry that functional parent doctrines will create or exacerbate conflict and instability in children’s lives. 60 See Katharine K. Baker, Equality and Family Autonomy, 24 U. Pa. J. Const. L. 412, 443, 465 (2022) [hereinafter Baker, Equality] (noting that “[w]hen the judicial system inserts itself into parental decision-making[,] . . . the results are at best ineffective and at worst catastrophic for children, parents, and the polity”). This observation also relates to the concern that, without biological connection and formal ties anchoring parenthood, the number of parents for any one child is without limit. See, e.g., Jacqueline V. Gaines, The Legal Quicksand 2+ Parents: The Need for a National Definition of a Legal Parent, 46 U. Dayton L. Rev. 105, 121–22 (2021) (“The legal recognition of more than two parents . . . further stretches the child’s time between multiple households. As a result, there will be potentially three or more houses that the child is shuttled to and from.” (footnote omitted)); Elizabeth A. Pfenson, Too Many Cooks in the Kitchen?: The Potential Concerns of Finding More Parents and Fewer Legal Strangers in California’s Recently-Proposed Multiple-Parents Bill, 88 Notre Dame L. Rev. 2023, 2060 (2013) (“Children may be more harmed than benefited by maintaining relationships with multiple adults because a child can only be emotionally dependent on a limited number of people.”). We respond to these arguments in another article. See Joslin & NeJaime, Multi-Parent Families, supra note 54, at 2582–85 (describing multi-parent cases based on our West Virginia data); see also Courtney G. Joslin & Douglas NeJaime, The Next Normal: States Will Recognize Multiparent Families, Wash. Post (Jan. 28, 2022), (on file with the Columbia Law Review) [hereinafter Joslin & NeJaime, The Next Normal].

These assumptions about who functional parent claimants are, how their claims arise, and what effects the claims have on children support normative arguments against using function as a basis for assigning paren­tal rights and responsibilities. Based on these assumptions, critics claim that the doctrines are unnecessary, intrusive, unwieldy, unpredictable, and wrongheaded. 61 See infra Part II. Although framed as normative objections, these diverse criticisms rest on empirical claims or assumptions about what the doctrines do or what they will do if adopted. 62 See infra Part II.

At times, empirical claims about functional parent doctrines are made without citation to significant evidentiary support—as though the doctrines are novel and thus that we do not, and could not, know how they apply. 63 See, e.g., Robin Fretwell Wilson, Undeserved Trust: Reflections on the ALI’s Treatment of De Facto Parents, in Reconceiving the Family: Critical Reflections on the American Law Institute’s Principles of the Law of Family Dissolution 90, 100 (Robin Fretwell Wilson ed., 2006) [hereinafter Wilson, Undeserved Trust] (“[O]ne can easily imagine that the rights the ALI seeks to confer on Ex Live-In Partners could be exploited not as an opportunity to stay in the children’s lives, but as an opportunity to control a child or her mother.”). Even when sources are cited, commentators tend to rely on a hand­ful of cases without providing grounds for concluding that those cases are representative. 64 See, e.g., Baker, Quacking, supra note 44, at 145–59 (drawing primarily on cases involving same-sex couples). Ultimately, the burgeoning debate over functional parent doctrines operates largely at the level of speculation or unsupported generalization.

This need not be the case. Functional parent doctrines have long existed, offering ample evidence to collect and examine. 65 Our study begins in 1980, but some of the doctrines predate that starting point. See, e.g., Spells v. Spells, 378 A.2d 879, 882 (Pa. Super. Ct. 1977) (explaining the state’s in loco parentis doctrine and observing that a “stepfather who lives with his spouse and her natural children may assume the status ‘in loco parentis’”); D’Auria v. Liposky, 177 A.2d 133, 137 (Pa. Super. Ct. 1962) (remanding for new trial to determine whether longtime foster parents stood in loco parentis). This Article develops a more thorough, detailed, and accurate account of functional parent doctrines in action. It also provides data with which to assess the empirical assumptions that pervade accounts of functional parent doctrines. Rather than LGBTQ parents representing the dominant class of claimants, relatives constitute the largest share of functional parents in the data set. Rather than post-dissolution custody disputes overwhelmingly predominating, the data set includes a range of scenarios that give rise to functional parent claims, including cases involving parental death and child welfare intervention. Rather than finding that courts use functional parent doctrines in ways that disrupt and unsettle children’s lives, our study finds that courts typically apply the doctrines in ways that secure children’s relationships with the individuals who are in fact parenting them. In a large swath of cases in the data set, protection of the functional parent–child relationship does not fundamentally alter the existing dynamic between the biological or legal parent and the child. 66 In this Article, the term “legal parent” generally describes a parent of the child other than the functional parent. Three caveats: First, in most cases, the legal parent is also the biological parent, and so at various points, and in reference to specific cases or scenarios, we use the term “biological parent.” But we do not mean to suggest that all biological parents are legal parents, or vice versa. To the contrary, some legal parents are not biological parents, and some biological parents are not legal parents. Second, if a court adjudicates a person to be a functional parent, in some jurisdictions, as we describe in Part I, that person would also be a legal parent. Third, in a few cases, a biological parent is seeking to be adjudicated a functional parent. These cases typically involve either a biological parent whose parental rights had been terminated but who continued to have a relationship with the child, or a person who was a gamete donor and thus could not establish parentage based on a biological connection. Instead, courts in our study routinely apply the doctrine in ways that preserve the child’s existing living arrangement with the person who is serving as their primary caregiver. 67 See infra section III.D. In short, evidence from our study does not lend significant support to the assumptions on which skepticism of functional parent doctrines often rests. 68 See infra Parts III–IV.

Not only do our data not support the empirical assumptions that undergird normative objections to functional parent doctrines, but our data lend support to arguments in favor of functional parent doctrines on child-centered grounds. 69 See infra Part V. Scholars have traditionally invoked children’s interests as the justification for functional parent doctrines. See, e.g., Joseph Goldstein, Anna Freud & Albert J. Solnit, Beyond the Best Interests of the Child 27 (1973) (“Where legal recognition is withheld from [the psychological parent–child relationship] and the child removed, the forcible interruption of the relationship . . . is reacted to by the child with emotional distress and a setback of ongoing development.”); Martha Minow, Redefining Families: Who’s In and Who’s Out?, 62 Colo. L. Rev. 269, 284 (1991) (defending “the functional test as a way of achieving the child’s interests”). Our study shows how the doctrines are applied by courts to preserve relationships between children and their primary caregivers. 70 See infra Part V. In doing so, judicial application of the doctrines routinely makes children’s lives more stable and secure, not less. 71 See infra Part V. Ultimately, this Article’s examination of how functional parent doctrines operate on the ground can reorient the normative debate over these doctrines in both academic and lawmaking domains.

This Article proceeds in five Parts. Part I describes existing functional parent doctrines, offering a more comprehensive and accurate account than currently exists. This Part shows that functional parent doctrines are more widespread than commonly understood and that they are not a red-state or a blue-state phenomenon. Instead, they appear in two-thirds of U.S. jurisdictions—jurisdictions that are politically and geographically diverse. Part II describes the empirical study, explains key limitations, and reports some general findings. Because the data set includes only electronically available decisions, we do not make claims about the universe of litigated functional parent cases or about the role of functional parent doctrines in disputes that never reach court. Instead, we report findings regarding the available decisions. Part III focuses on specific aspects of the data, examining the identities of functional parents, the roles that functional parents play in children’s lives, the contexts in which functional parent claims arise, and how courts adjudicate functional parent claims. Part IV draws on our empirical study to evaluate some of the concerns that scholars, judges, and advocates have raised about functional parent claims. This Part shows that our data do not offer significant support for many of these concerns. Finally, Part V explains how our empirical analysis lends support to functional parent doctrines on child-centered grounds.

The insights offered by this Article come at a particularly critical moment. Families that include nonbiological, nonadoptive, and nonmarital parent–child relationships have long been a feature of American households. 72 For example, from the 1870s to 1940s, between 7% and 10% of American children lived in multigenerational households. Natasha V. Pilkauskas, Mariana Amorim & Rachel E. Dunifon, Historical Trends in Children Living in Multigenerational Households in the United States: 1870–2018, 57 Demography 2269, 2277 (2020).
Anthropologists, as well as researchers in other disciplines, have long observed “alloparenting” in human populations—“caretaking from individuals other than an offspring’s mother.” J.S. Martin, E.J. Ringen, P. Duda & A.V. Jaeggi, Harsh Environments Promote Alloparental Care Across Human Societies, 287 Proc. Royal Soc’y B 1, 1 (2020) (“Alloparental care is central to human life history, which integrates exceptionally short interbirth intervals and large birth size with an extended period of juvenile dependency and increased longevity.”); see also James K. Rilling, The Neural and Hormonal Bases of Human Parental Care, 51 Neuropsychologia 731, 732 (2013) (“Humans are an alloparental species, meaning that although mothers are usually the primary caregiver, they typically receive help from fathers, grandmothers, sisters, brothers, older children, etc.” (citation omitted)).
Contemporary circumstances, however, amplify the significance of these relationships. A number of demographic trends—including increasing rates of nonmarital child-rearing and cohabitation—have resulted in greater numbers of children being raised by individuals other than their biological parents. 73 Pilkauskas et al., supra note 72, at 2272. In addition, a range of different forces—from the opioid epidemic to the COVID-19 pandemic—have resulted in relatives, including grandparents, taking on caregiving roles at increasing rates. 74 See Christina J. Cross, Extended Family Households Among Children in the United States: Differences by Race/Ethnicity and Socio-Economic Status, 72 Population Stud. 235, 247 (2018) (“[O]ver one in three youth spend some time in an extended family before age 18.”). In light of these developments, understanding how functional parent doctrines operate in practice is especially pressing.