The association between childhood family structure and offspring well-being is well-documented. Recent research shows that adult children of divorced parents will likely marry someone whose parents’ divorced (i.e., family structure homogamy) and are subsequently likely to divorce themselves. This literature has focused primarily on marital unions, despite the rise in cohabitation and nonmarital childbearing. Research suggests that marriage and cohabitation are different types of unions and have different implications for the well-being of children. Therefore, we extend the literature by examining the role of family structure homogamy in matching patterns and union stability among unmarried, cohabiting couples. Data from the Fragile Families and Child Wellbeing Study suggest that unmarried, cohabiting mothers and fathers are both more likely to be from nonintact childhood family structures and are significantly more likely to dissolve their unions compared to married parents who both tend to be from intact childhood family structures.