According to the question, Amit's sister's mother's husband is Gagan's daughter's mother's husband's father. Sister's mother is mother. Daughter's mother is wife. ⇒ Amit's mother's husband is Gagan's wife's husband's father. Mother's husband is father. Wife's husband is Gagan himself. ⇒ Amit's father is Gagan's father. ∴ Amit is the brother of Gagan.