This analysis of the American Law Institute\u27s Principles of Family Law, Chapter 3, examines how the Principles perceive the origins and extent of parental obligation. What is that makes someone financially responsible for a child? Perhaps surprisingly, the Drafters of this key chapter of the Principles spend remarkably little time analyzing that question. Instead, to determine who has parental obligation, the Principles rely on extant legal paternity and parenthood doctrine that is itself completely muddled. To determine the extent of parental obligation, the Principles employ a binary biological ideal of parenthood that fails to reflect reality for close to half of the children in this country. What is most striking about this tradition...