While introducing a man to her husband, a woman said his brother's father is the only son of my grandfather. How is the woman related to this man?

Start with the phrase that carries the whole question: the only son of the woman's grandfather. That only son is her father, so the woman's father is her grandfather's only son.

The statement then says the man's brother's father is this same person. Two brothers share a father, so the man's brother's father is the man's father too. That makes the man's father and the woman's father the same person.

Children of the same father are siblings, so the woman is the man's sister. Option B is correct.

• A) Aunt: an aunt is a parent's sister. Here the woman is a child of the man's own father, so she is not his aunt.
• C) Mother: a mother is a parent. The woman shares the man's father, so she is his sibling, not his parent.
• D) Daughter: a daughter is a child. The man's father is the woman's father, so the man is her sibling, not her parent.

The core concept is blood-relation decoding, where you convert each clue into a family link and then trace the chain step by step. This same skill carries over to the Reasoning section and to family-based clues in case studies on social issues.

Trap: aspirants often treat the man as the brother's father, or read the grandfather's only son as an uncle. Trace the father link first and the answer follows.