Taking advantage of recent data that permit an assessment of the importance of extended household members in operationalizing the relationship between family structure and children’s early development, this study incorporated coresident grandparents, other kin, and nonkin to investigate the associations between extended household structure and U.S. children’s cognitive and behavioral outcomes at age 2. Analyses assessed whether these relationships differed for Latino, African American, and White children and tested four potential explanations for such differences. Nationally representative data came from the Early Childhood Longitudinal Study-Birth Cohort of 2001 (N ≈ 8,450). Extended household structures were much more prevalent in households of young African American and Latino children than among Whites. Nuclear households were beneficial for White children, but living with a grandparent was associated with the highest cognitive scores for African American children. Nuclear, vertically extended, and laterally extended households had similar associations with Latino children’s cognitive and behavior scores. Results suggest that expanded indicators of household structure that include grandparents, other kin, and nonkin are useful for understanding children’s early development.