Despite the large number of children in stepfamilies, there is little research on the implications of large families for child well-being. This paper used three traditionally representative data sets--the National Commission on Children Survey (NCC), the National Survey of Families and Households (NSFH) and the National Survey of Children (NSC)--to examine the relationship between family type and parental time allocation to children and their activities and parental time constraints, and the impact of parental time investment and parent-child relationship on child well-being. NCC results revealed that stepparents, particularly of girls, were less likely than parents in intact families to attend religious services, help with special projects, and attend plays, concerts, or sports events. Compared to parents in intact and single-parent families, NCC stepparents and stepsons were less likely to rate their relationships as excellent or extremely close. Stepparents of NSFH boys were less likely to regularly attend church and church social events than those in intact families, and stepparents of girls were less likely to be a leader of a religious group; eat breakfast regularly with daughters; attend school meetings regularly; or attend church. NSC revealed few family type differences in parental time and emotional investments in children. Differential parental time investments and religious participation partially explained behavior problems among NSFH children. Although being in a stepfamily did not affect NSC males' behavior problems, closeness of the parent-child bond mediated the effect of living in a stepfamily on girls' behavior problems. Children in single-parent families, especially boys, had the most adverse outcomes. (KB)