What type of family structure is formed when a young couple invites the wife's widowed mother to live with them?

The situation described illustrates the concept of an extended family structure. An extended family is a family unit that includes not just the parents and their children but also other relatives, such as grandparents, aunts, uncles, or in this case, a widowed mother. By inviting the wife's mother to live with them, the couple is creating a living arrangement that goes beyond their immediate nuclear family, which consists solely of parents and their offspring.

In a nuclear family, the structure would be limited to just the parents and children, excluding any other relatives. A single-parent family consists of one parent raising one or more children without the presence of the other parent. A blended family arises when two families unite through marriage or partnership, typically involving children from previous relationships. Therefore, the establishment of a living arrangement that includes the wife's mother aligns best with the definition of an extended family.