Why do authoritative kinship groups endure after states engage in nation building? What role does authoritative kinship play in the nation building process? Kinship is the genuine belief in a familial connection between members of a group, usually denoted in terms of a common ancestor. While many existing explanations of identity treat authoritative kinship as the creation of colonial powers (Herbst, 2000; Posner, 2005), less has been written about cases where colonial intervention mediated, but did not determine the salience of authoritative kinship during nation building. New constructivist understandings of identity formation treat kinship as a descent-based attribute activated in different social and political contexts (Chandra, 2012). I argue that differences in the construction of kinship before nation building account for variation in the endurance of authoritative kinship structures. Nation building requires states to create new political identities for their residents. However, authoritative kinship groups resist such change because kinship is a “sticky” identity: it denotes not only a person’s national in-group, but position within that in-group. To explain this endurance, I model kinship as either “personal” or “impersonal.” Impersonal kinship means two people in an authoritative kinship structure mutually recognize each other as “relations” - descendants of a common ancestor. Such a relationship is similar to that between “co-ethnics” but with the added requirement of genuine belief in a mutual relation to one shared ancestor. In contrast, personal kinship means two people in an authoritative kinship structure mutually recognize each other as “cousins,” related through both a common ancestor and a more immediate relation. I hypothesize that where kinship ties are primarily personal, authoritative kinship structures exhibit high endurance through nation building. In contrast, where kinship ties are conceptualized as primarily impersonal, kinship structures exhibit low endurance. I test this hypothesis with a most-different case comparison based on fieldwork in Kuwait and Oman, including five months of archival research (10 British archival sets, 2 newspaper archives, and 15 Arabic-language books on the Gulf) and approximately 40 interviews with experts and members of authoritative kinship structures. Kuwait and Oman share a history of pre-existing authoritative kinship structures. However, Kuwaiti kinship ties are personal, while Omani ties are impersonal. In the paper, I suggest this variation explains differences in the endurance of authoritative kinship structures in each state, and discuss the effects of these structures on the creation of new political identities during nation building.