The demographic transition is also a kinship transition. This insight is obvious for certain types of kin—as fertility falls, parents have fewer children, for instance—but its broader implications for communities remain unexplored. Prior work on this topic has focused on how the demographic transition reshapes the availability of living kin within a society over time to the neglect of how differences in the demographic transition lead to differences in kinship networks between communities. In this article, I examine survey data (for rural Thailand) and use microsimulation methods to test how different pathways through the demographic transition affect kinship networks in communities. My results show that different routes through the demographic transition can substantially alter kinship network size and, entirely through the mechanism of demographic change, have indirect effects on community integration. These effects persist long after the demographic transition has ended. I theorize reasons that community‐level differentiation in kinship networks owing to the demographic transition are an important mechanism linking the demographic transition to modernity.