Step 1: Understanding the given information
- There are 4 adults: A, B, D, E.
- There are 3 children: C, F, G.
- F and G are girls.
- A and D are brothers.
- E is married to one of the brothers and has 2 children.
- B is married to D and G is their child.
Step 2: Determining marriages and children
- Since B is married to D, E must be married to A.
- E has 2 children — since F is a girl and already known as a child, C must be the second child of A and E.
Step 3: Gender and relation of C
- F is a girl, so the other child (C) can be either a boy or a girl. The question implies C is not one of the two named girls (F and G), so C must be a boy.
- Therefore, C is A’s son.
\[
\boxed{\text{Answer: (D) A’s son}}
\]