Investigated effects of divorce and family relations on young children's development in ethnically diverse low-income families. Found that soon-to-be-divorced families demonstrated higher rates of preschool-age behavior problems, and already-divorced families showed similar trends. Parental conflict and behavior problems accounted for pre-divorce child-behavior-problem differences. Rejecting parenting accounted for problem behavior differences between always single-parent and always two-parent families. (Author/KB)