To resolve this, we must decipher Seema's family description and determine the man's relation to her.
- Family Relationship: A logical inference of familial connections derived from provided statements.
- Mother's Only Son: Indicates Seema possesses a single brother (assuming she is not an only child).
- Brother of that Son: Refers to another male individual within Seema's family structure.
Statement: “He is the brother of my mother’s only son.”
- Seema's mother's only son equates to Seema's brother.
- The individual in question is the brother of Seema's brother.
Given that the man is the brother of Seema's brother, he is consequently also Seema's brother.
The man is Seema’s brother.