Most of us become citizens at birth based either on our birthplace or our parents’ citizenship status. Over thirty countries recognize birthplace citizenship, but inherited citizenship is nearly universal. Such universal legal rules are rare, and they are particularly remarkable in the context of citizenship, where state sovereignty is near its apex. This article explores why inherited citizenship is necessary, even in nations recognizing birthplace citizenship. It surveys the history, definitions, purposes, current rules, politics, and global trends in this area and identifies three modern categories of birthright citizenship laws: primary inherited citizenship systems, dual inherited and birthplace systems, and hybrid birthright systems. It also examines some foundations of property inheritance laws and family law concepts to illuminate the deep connections between the doctrines of property, family, and citizenship inheritance. Hopefully, in the process, it will enlighten the ongoing U.S. debate regarding birthplace citizenship, a discussion that has rarely considered the role of inherited citizenship, which is the other half of our dual birthright citizenship system.