Family is one of the key loci of transition to adulthood projects. It is both a focus of transition, that is, developing new relationships between family members as one becomes an adult, and a support though which other transitions can be achieved, for example, living independently and entry into world of full-time work. Although it is consistent with action theory to expect a multitude of transition-related joint actions, projects, and communication to occur across the family system and sub-systems within the family, empirical research using the action-project method to study family transition-to-adulthood projects has focused exclusively on the parent–youth sub-system. Thus, it is this sub-system that is the focus of this chapter. However, it is important to understand that other family relationships can be just as important. For example, when the youngest child in a family begins her transition to adulthood, joint transition projects with an older sister are likely to be a vital part of her transition process.