Using 24 years of data from the March supplements to the Current Population Survey and detailed categories of family structure, including cohabiting unions, I assess the contribution of changes in family structure to the dramatic rise in family income inequality. Between 1976 and 2000, family structure shifts explain 41% of the increase in inequality, but the influence of family structure change is not uniform within this period or across racial-ethnic groups. In general, the estimated role of family structure change is inversely related to the magnitude of the changes in inequality. Furthermore, by including cohabitation, I find lower levels of total inequality and a weaker role for demographic shifts in family structure for trends in income inequality.