Explanation:

- Let's break down the family relations:

- A is from the first generation.

- E is A's daughter-in-law, married to A's son I, who is the father of G.

- B is the son of E, making B and G siblings.

- C is married to D. D is the son-in-law of H, and C and D are in the second generation.

- F is D's child, making F a third-generation member.

- G is the aunt of F, confirming D is the sibling of G.

- Only four males exist, so B, D, I, and an undetermined male fit this, but I is not married to C.

- Thus, B is the grandson of A.