With the increasing importance and prevalence of kin-state policies, this thesis identifies three gaps in existing kin-state research. Theoretically, existing literature focuses on how kin relations can induce or reduce conflict between states, overlooking the dynamics of interaction between kin-states and kin communities. Conceptually, existing literature focuses on kin communities as minorities, overlooking kin majorities. Methodologically, existing literature focuses on top-down institutional and state-level analyses of kin-state relations, overlooking bottom-up agency-centred perspectives. To address these gaps, the thesis develops a model of nested integration, to analyse relations been kin-states and kin majorities from a bottom-up perspective. Nested integration does not challenge the borders separating kin-state from kin communities, but affects the meaning of this border. The thesis examines the comparative explanatory power of this model of nested integration by generating evidence about the meanings of kin identification and engagement with different kin-state practices, through a cross-case comparison of Crimea vis-à-vis Russia and Moldova vis-à-vis Romania. These cases are selected from a wider kin majority typology as two contrasting examples of kin-state policies: Romanian citizenship in Moldova and Russian quasi-citizenship Compatriot policy in Crimea. Overall, the thesis argues that Moldova exhibits more nested integration than Crimea because of the type, legitimacy and availability of kin-state provision, which the thesis argues is consequential for the degree of nested integration observed. The thesis also refines the model of nested integration, by taking account of empirical evidence, arguing for the importance of considering internal fractionalization within the kin majority, social dependence and geopolitical dependence. Incorporating these elements within the model shows kin-state relations to concern not only issues of identity, but also security, public goods provision and geopolitical region-building narratives. These elements have been overlooked by existing research and demonstrate the importance of a bottom-up, agency-centred and comparative perspective for kin-state scholarship.