In this paper I analyze the value system of the Islamic State, the armed group that took control of large parts of Syria and Iraq in the 2010s, in light of anthropological kinship and descent logic. IS sought to rapidly build its own citizenry within the territory it controlled. This paper takes its claim to be a “state” seriously. This state arose rapidly and in very public fashion, spreading its vision and message in social media and various other forms of media, and through the use of violent public spectacle that made its way into conventional news sources such as television and print. IS rampaged through the areas it sought to control, and came to control, committing violent acts that have been labeled “genocide” by several other governments. I interviewed some of its victims/survivors in Iraq in 2015. These interviews and public sources suggest that IS sought to build a citizenry that constituted a uniform nation that adhered closely to its value system, and that it did so not simply by promulgating its own “Islam” as it claimed, but through means that addressed issues of succession and citizenry-building. In patrilineal descent systems, new members of groups (whether small family groups or larger political groups) can be “made” through conception. An infant who is conceived by a male member of the group is automatically deemed a member of the group. The IS was well-known to have used the abduction and rape of women as a means to instill fear and win its battles. I argue, however, that abduction and rape were much more than strategic tools in conflict: they were well-thought-out strategies at quickly building a loyal citizenry comprised of the resulting offspring. While their mothers were subjugated and may or may not have come to agree with IS doctrines, the children conceived by IS rape victims were easy fodder for indoctrination. Recruiting adults to a cause is one way to build a new group, but raising children who are taught a group’s values within a tightly-controlled space is another way. This paper analyzes some of the ways in light of the patrilineal kinship model elucidated by sociocultural anthropology. Patriliny is common worldwide and its social outcomes diverse, but this case showcases how a descent system such as patriliny can be harnessed to provide logical impetus to violent and coercive state-building.