Family structure is a term used to describe the way in which a family is organized. It typically includes the roles and relationships between parents, children, and other relatives. The most common family structure is the nuclear family, which consists of two parents and their children. Other family structures include extended families, single-parent families, and blended families. The term 'tree' is often used to refer to family structure, as it can be seen as a metaphor for the way in which family members are connected.