Study the following information carefully and answer the question given below.…

Concept

In a blood-relation puzzle, never jump to a label. First fix each person's GENERATION and GENDER from the clues, then connect couples and parent-child links. A reliable rule: a man is the brother-in-law of an unmarried woman only when he is the husband of that woman's sister (he cannot be her spouse's brother, because she has no spouse). Once couples and parents are fixed, a relationship two generations up the same line is a grandparent link.

Application (build the family tree step by step)

1. A is the brother-in-law of F, and F is not married. So A is not the brother of F's husband (F has none) - A must be the husband of a SISTER of F.

2. F is the sister of G, so G is a sibling of F. The only sister of F available to be A's wife is G, so G is female and A is married to G. (A, G) form a couple.

3. A is the father of B, so B is a child of the couple A and G.

4. B is the wife of D, so B and D form the next-generation couple.

5. C is the granddaughter of G. Because A and G are the same couple, C is equally A's grandchild, and C reaches that generation through B (A and G's child).

6. Trace the line A and G -> their child B (married to D) -> their child C. That is exactly two generations from A down to C.

A is two generations directly above C on the same family line, and A is male, so A is the grandfather of C.

Cross-check

• The label one generation up (a parent of C) does not fit: A is the parent of B, and B is the parent of C, so A sits one level higher than a parent.

• A same-generation label (a sibling of C) is impossible: A belongs to the oldest of the three generations while C belongs to the youngest.

• A side-branch elder label (a parent's brother of C) does not fit either: A is on C's direct ancestral line through B, not on a collateral branch.

• Counting generations A -> B -> C confirms exactly two steps down a direct line, which is the grandparent relationship. Result: grandfather.