If A is the brother of B; C is the father of A; D is the wife of C; what is D…

Concept: In blood-relation puzzles, the wife of a person's father is that person's mother — marrying the father places a woman in the parents' generation as mother to all of his children, regardless of how many children he has.

Application: A is the brother of B, so A and B are siblings who share the same parents. C is given as the father of A, and since A and B share parents, C is also the father of B. D is the wife of C, so by the concept above, D is the mother of C's children — that is, of both A and B.

• Sister — would require D to be another child of the same parents as B; instead D is described as C's wife, one generation above B, not a sibling.

• Aunt — is the sister of one of B's parents, not the parent's spouse; D's link to the family comes through marriage to C, not through being a sibling of either parent.

• Cousin — descends from a sibling of one of B's parents, one generation removed from B; D instead is married directly to B's father, placing her in the parents' generation itself.

So, matching the given facts, D is the mother of B.