Drawing on interviews with 16 lesbian mothers and co-parents, this paper considers the tension between law's recognition of the social and genetic aspects of parenting. Through findings from the interviews, it will be demonstrated that law remains unable to distinguish adequately between different dimensions of parenthood, and the rights and responsibilities that should be attached to each. The innovative approach lesbian parents take to defining and practicing parenthood is considered and it is suggested that some way of separating legally the fact of genetic parentage from the act of social parenting would be beneficial for all families.