Family relationships across several generations are becoming increasingly important in American society. They are also increasingly diverse in structure and in functions. In reply to the widely debated “family decline” hypothesis, which assumes a nuclear family model of 2 biological parents and children, I suggest that family multigenerational relations will be more important in the 21st century for 3 reasons: (a) the demographic changes of population aging, resulting in “longer years of shared lives” between generations; (b) the increasing importance of grandparents and other kin in fulfilling family functions; (c) the strength and resilience of intergenerational solidarity over time. I also indicate that family multigenerational relations are increasingly diverse because of (a) changes in family structure, involving divorce and stepfamily relationships; (b) the increased longevity of kin; (c) the diversity of intergenerational relationship “types.” Drawing on the family research legacy of Ernest W. Burgess, I frame my arguments in terms of historical family transitions and hypotheses. Research from the Longitudinal Study of Generations is presented to demonstrate the strengths of multigenerational ties over time and why it is necessary to look beyond the nuclear family when asking whether families are still functional.