This article analyzes how union patterns in Mexico and Colombia affect the lives of children. The proportion of children affected by a disruption by the age of 15 is estimated by using life table methods. The factors that contribute to a child’s risk of experiencing a disruption are investigated by using proportional hazard models. Finally, the living arrangements of children by the mother’s marital status, the urban status, and the mother’s educational attainment are explored. The findings indicate that about one-fifth of Mexican children and one-third of Colombian children spend some time with an unmarried mother by the age of 15. In addition, those who experience a disruption or are born outside of a union spend a considerable length of time in the single-parent state. Most children of an unmarried mother live in an extended-family household, often with a grandparent.