In recent decades millions of people have migrated to the democracies of North America and Western Europe. Some of these immigrants have become citizens of their new homelands, while others remain foreign residents. This article shows that the family context shapes decisions over naturalization. The costs and benefits of becoming a citizen of one’s country of residence depend, in part, on the naturalization decisions of immediate family members. The article draws on evidence from interviews and census data in Austria, and extends the analysis to the USA in order to test the scope for the argument to generalize. I conclude by discussing what family-level dynamics in naturalization can teach us about the concept of citizenship.