East Asian societies have a patri-lineal tradition in which a family successor must be a son and parents live with the heir and his family. In Japan, the patri-lineal family system was prevalent among the samurai warrior class in the early modern period. In the modern period, it was stipulated in the civil code until the end of World War II. This tradition, however, is changing with a background of gender equalization and fewer number of sons resulting from low birth rates. Intergenerational Relationships between Married Children and Their Parents in 21st Century Japan is the first book that introduces a new perspective of the individualized marriage into a study of intergenerational relationships and examines how the patri-lineal tradition is both changing and maintained. This book deals with patri-local coresidence, matri-local nearby-residence, and support exchange between adult children and their parents/ parents-in-law, and offer a new framework for comparative studies of today’s East Asian families.