Historically sons-in-law (giri no musuko) have been marginal in family structure in Japanese household compositions; however, changes in parents-children relationships, demography, marriage patterns, ageing, child-care, residential patterns, gender roles, and so forth as well as the decline of Confucian worldviews result in the son-in-law being more central within family relations. An important shift is towards parent-child relations based more on intimacy, particularly with daughters, than filial duty. Stronger parent-daughter links result in sons-in-law becoming more central in family relations. In this new family situation social expectations for the son-in-law relationship, between the husband and the wife's parents, are not well-formed. Thus I focus on the son-in-law relationship to provide a window through which to consider changes in Japanese familyhood and masculinity, particularly fatherhood - how family is 'related'. Specifically, I consider how the son-in-law relationship is negotiated in daily practices and how this relationship contributes to understanding inter-generational issues of child and elderly care. My contribution to the literature is three-fold. First, I place focus on the daily practices underpinning a family relationship, between parents and son-in-law, that is traditionally marginal but of increased importance in contemporary times. Second, in contrast to the recent focus on nuclear families and individuals in the family, I consider the contemporary family from a broader perspective, as focusing on a relationship that is part of the extended family and not as an isolated domain. Third, I provide a perspective on manhood in the domestic sphere, which to date has received limited attention in the Japanese Studies literature but now merits attention as men have recently increased their involvement in the domestic matters. My methodology involves a mix of research methods with a main emphasis on fieldwork based on narrative interviews.