What is defined as partners living together, which could be either long-term or short-term?

The term that best describes partners living together, regardless of the duration of their relationship, is indeed "unmarried family." This concept encompasses various living arrangements where individuals may share a household and a significant emotional bond without being legally married.

This definition allows for a wide range of relationships, from those that are established for a long-term commitment to more casual or temporary arrangements. As societal norms have evolved, the structure of families has diversified, making the term "unmarried family" particularly relevant in contemporary discussions surrounding family dynamics and legal considerations.

The other terms refer to different family structures. A nuclear family typically consists of two parents and their children living together, a blended family involves two parents from previous relationships forming a new family unit that includes children from those relationships, and an extended family includes additional relatives beyond the nuclear unit, such as grandparents, aunts, and uncles. Each of these definitions emphasizes a particular type of familial arrangement, distinct from the broader and more inclusive idea of an unmarried family.