What characterizes a sole parent family?

A sole parent family is characterized as a family where a single parent is responsible for raising their child or children. This typically means that the parent may bear the sole legal and financial responsibility for the children, often as a result of circumstances such as divorce, separation, or the death of a partner. In this family structure, the focus is on the dynamics and challenges faced by the parent and their children, including the emotional and financial aspects of single parenting.

The other options do not fit this definition. They refer to family structures that involve both parents or specific conditions that do not align with the essence of a sole parent family, such as having children over 18 or being an adoptive parent without biological children.