Transnational children—ranging from infants to teenagers—reside in, and migrate to and from, both Mexico and the United States. This paper considers this understudied population, the youngest members of Mexican migrant communities, to understand shifting configurations of kinship in a transnational space. By focusing on transnational families with ties to San Luis Potosí and several locales in the U.S. Southwest, I study the everyday experiences of Mexican migrants to demonstrate the presence and power of the U.S. state in family life. This paper examines a dilemma in transnational lives: a primary motivation for migration is to support and benefit children, and yet children are repeatedly in precarious or threatening situations precisely because of transnational movement, their own and that of their family members. The inclusion of children in the study of transnationality, I argue, nuances our understanding of the (re)production and (re)structuring of kinship. Moreover, a focus on children as embedded within families problematizes popular conceptions of migrants as solely autonomous agents, uncovering the multiple ways in which the actions of parents, children, and other family members are repeatedly shaped and constrained by state policies. [Keywords: transnationalism, children, Mexico, transnational children, migrants, migration]