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?

Let's analyze the statement step-by-step: Suresh says:
"He is the son of the only son of my mother."

• "My mother" refers to Suresh's mother.
• "The only son of my mother" means Suresh himself (since he is the only son).
• So, "the son of the only son of my mother" means "the son of Suresh."

Therefore, the boy in the photograph is Suresh's son.

Conclusion:

Suresh is the father of that boy.