If X is the brother of the son of Y's son, how is X related to Y?

Grandson

The correct answer is Option (1) → Grandson

To solve this blood relation puzzle, let's break the description down step-by-step, starting from the end of the sentence:

1. "Y's son": This is simply a son of Y.
2. "Son of [Y's son]": The son of a person's son is their Grandson.
3. "Brother of [the Grandson]": The brother of a grandson is also a Grandson.

The Breakdown

• Y is the grandparent.
• Y's son is the parent of the child.
• The son of Y's son is Y's grandson.
• X is the brother of that grandson, making X also the grandson of Y.

Answer: X is the Grandson of Y.