In this highly original work, renowned family and contract law expert Brian H. Bix explores the increasing legal recognition of private ordering in American family law. Today, individuals can alter the terms of a marriage and divorce through agreements, and courts sometimes allow individuals to create, waive, and alter parental rights by way of surrogacy, open adoption, and co-parenting agreements, among other mechanisms. But when is such private ordering beneficial to all, and when should it be regulated or prohibited? Families by Agreement explores these questions in accessible detail to provide an important resource for those who litigate in these areas and for those who want to be thoughtful participants in these moral and policy debates.