This book is written for academics, students, policymakers, practitioners, and non-governmental organisations interested in the legal recognition of LGBT+ parenting. The book presents arguments in favour of the legal recognition of gay and lesbian families that are based on consideration of the best interests of the child. In this context, 'best interests' is informed by reference to children's rights and to social science data. Applied in this manner, it is argued that the best interests of children can be used to demand that same-sex parenting arrangements are afforded legal recognition and protection. Suggestions are also presented as to the most appropriate manner of providing for this recognition in the areas of parental responsibility, adoption, donor-conception and surrogacy. These suggestions are drawn from comparative case studies, focusing on England and Wales, Ireland and South Africa, that are used to facilitate assessment of the best interests principle.