Migration changes how families form and dissolve, and how one should conceptualize the family. This has implications for thinking about how the migration decision is modelled when individuals are unable to picture the counterfactual families they may have. Differences in marital status can induce two otherwise identical individuals to make different migration decisions. It also has implications for attempts to causally estimate impacts of migration, when the family composition changes with the migration decision itself. This paper shows empirically that changing marital status after migration is widespread, and that the traditional model of a fixed family sending off a migrant who remains part of that same family only describes a minority of migrants moving from developing countries to the U.S. The authors draw out lessons from thinking about counterfactual families for empirical research and for migration policy.