100 S. Titshaw corrected by federal reinterpretation of its rules to rely on family law parentage determinations.7 Rather than misplaced reliance on family law, the problems Dumbrava and Bauböck describe regarding the application of ius sanguinis following ART are consequences of outdated family law or of international conflict-­ of-­law issues where relevant jurisdictions define parentage differently. To the extent that the problems stem from conflict-of-law issues, it is worth noting that the Hague Conference on Private International Law is currently exploring whether to draft a multilateral instrument on international parentage and surrogacy, which might resolve some issues.8 To the extent that the problems stem from outdated family law, the best solution is to fix the family law. Family law generally reflects a more individualized, in-depth understanding of parent-child relationships than do citizenship or migration laws. Based on long experience and empirical data, family law tends to favour the stability of permanent family relationships with commensurate duties and benefits in the best interests of children. By tending to ensure the same citizenship for children and their parent(s), ius sanguinis rules also generally promote stable solutions in the best interests of children in a way that less permanent migration rules do not. I agree with Bauböck that multiplicity of citizenships for children is generally not a problem, and I support his call for a more generous understanding of parenthood for purposes of citizenship transmission. But I would not opt for a ius filiationis proposal if it requires an entirely independent determination of social parenthood for citizenship transmission purposes. Officials dealing with citizenship issues are not as well suited to determine these issues as those administering family law. Also, too much generosity in this area might instigate cross-border mischief in familial disputes by ‘social parents’. 7 8 E.U.’, in C. Casonato & A. Schuster (eds.), Rights on the Move: Rainbow Families in Europe: Proceedings of the conference: Trento, 16–17 October 2014, Trento: 189–200 (194-9). Trento: Università degli Studi di Trento, Facoltà di Giurisprudenza, available at http://eprints.biblio.unitn.it/4448/ Titshaw, S. (2013), ‘Revisiting the Meaning of Marriage: Immigration for Same-Sex Spouses in a Post-Windsor World’, Vand. L. Rev. (66): 167–177 (174–75), available at http://www.vanderbiltlawreview.org/2013/10/ revisiting-the-meaning-of-marriage-immigration-for-same-sex-spouses-in-apost-windsor-world. At: http://www.hcch.net/upload/wop/gap2015pd03a_en.pdf