In collateral lines, which of the following is a 3rd-degree relationship?

• A. Brother and sister
• B. Uncle and niece
• C. First cousins
• D. Grandparent and grandchild

Answer: (B)

In collateral kinship, the degree is the sum of generations each person is removed from their nearest common ancestor. A third-degree relationship means there are three generations separating the two people from that shared ancestor.

An uncle and niece share a grandparent as their nearest common ancestor. The uncle is one generation away from that grandparent, while the niece is two generations away. 1 + 2 = 3, so they are a third-degree collateral relationship.

By contrast, brother and sister are both one generation from the parent, giving two generations total (second degree). First cousins are each two generations from the grandparent, totaling four generations (fourth degree). Grandparent and grandchild are in a direct line, not collateral, and are counted along the direct line (parent-child is first degree, grandparent-grandchild second).

Thus, the 3rd-degree collateral relationship here is uncle and niece.