This book offers a new perspective and empirical evidence that are relevant for understanding changes in family structures, intergenerational relationships, and female labor force participation in the “strong family� societies and that also shed light on those in the “weak family� societies. Focusing on the stem family and the gender division of labor, presenting detailed quantitative evidence, and testing the theories on family change and gender revolution, the book provides a comprehensive examination of change, continuity, and regionality in the Japanese family system over the twentieth century. By analyzing data from a nationally representative life course survey with event history techniques, it investigates factors affecting post-marital intergenerational co-residence and proximate residence along with those influencing continuous and/or discontinuous employment of married women across the life course. In this way, it reveals the mechanisms underlying the stem family formation and those behind married women M-shaped employment pattern. It further explores regionality in the Japanese family system, applying a demographic mapping method to data from a nationally representative community survey and official statistics. The mapping analyses demonstrate persistent geographical contrasts between two types of living arrangements (single-household versus multi-household) in the stem family accompanied by two types of maternal employment (full-time versus part-time). They also reveal a historical correlation between traditional communal parenting systems and modern childcare services, linking past to present from the late nineteenth to the early twenty-first century.