Final answer:
Kareem's living situation with his paternal grandmother is best described as an extended family, which includes other relatives beyond the immediate nuclear family unit.
Step-by-step explanation:
Kareem lives with his paternal grandmother. His father is incarcerated, and his mother disappeared long ago. Taking into account that his family doesn't fit the typical nuclear family model consisting of two parents and children, and that it also doesn't align with a single-parent or blended family structure, Kareem's living situation best fits the description of an extended family.
An extended family includes not just parents and children but also other relatives such as grandparents, aunts, uncles, and cousins. In the United States, there is a growing number of children living with grandparents or other relatives, often due to parental incapacity caused by issues like incarceration or abandonment. Therefore, Kareem lives in an extended family arrangement.