Household composition is traditionally regarded as exogenous in economic analyses. The migration literature typically assumes that the migration of a household member is not associated with further variations in co-residence choices. We rely on a large Mexican panel survey to provide novel evidence on the correlation between the occurrence of an international migration episode and additional changes in household composition. Migrant households have a 34.5 percent higher probability of receiving a new member within one year after the migration episode. Attrition is significantly higher among migrant households, and we provide suggestive evidence that this is due to the dissolution of the household of origin of the migrant, with all its members left behind joining another household. The endogeneity of co-residence choices has implications for survey-based measurement of migration flows, for the analysis of selection into migration, and for the effects of migration on the individuals left behind.