This chapter investigates the common presuppositions we make about legal parenthood – for example, the assumption that biological parents are legal parents by default in most jurisdictions. Looking back at some of the ways in which legal rules of parenthood have shifted in recent history, I show that these rules are often more tightly knit with legal structures surrounding marriage and other kinship structures, than with biological parenthood, particularly for men. I examine the problems faced by unmarried fathers who either do not know they have biological offspring or discover this too late to claim legal parental rights. I also discuss the role of the principle of ‘the best interests of the child’ and the conflicts that arise when laws motivated by the best interests of children are broken for the sake of the best interests of a specific child. I then focus on the regulation of adoption and surrogacy in order to illustrate the fragility of distinctions between these practices, in which the difference between parenthood and a criminal offence sometimes hinges on a couple of pieces of paperwork.