Final answer:
A person would be considered a part of both their mother's and father's family in a system of bilateral descent, which is the common pattern in places like the United States.
Step-by-step explanation:
In which type of descent would a person be considered both a part of their mother's family and a part of their father's family? The descent pattern that traces an individual's kinship through both the mother's and father's ancestral lines is known as bilateral descent. This system of descent is most common in modernized nations like the United States, where individuals count relatives from both their father's and mother's sides as family.
Unlike unilateral descent, such as patrilineal or matrilineal, where kinship is traced through only one side, bilateral descent includes both parents' families in the lineage. This is distinct from ambilineal descent, where a single line is chosen.