pointing to a photograph of a boy suresh said, he is the son of the only son of my mother. how is suresh related to that boy?

Suresh is the father of that boy. Explanation:

• “My mother” = Suresh’s mother.
• “The only son of my mother” = Suresh himself (he is his mother’s only son).
• “He is the son of the only son of my mother” = the boy is the son of Suresh.

So, Suresh is the boy’s father.