Pointing to a photograph, a man said, "I have no brother, and that man's father is my father's son." Whose photograph was it?

His Son

Before answering this question we must be aware of the method to solve the blood relation questions.

For example : 

It is now clear, how to make charts in Blood relations. Now, shifting to another type, in this we solve the question in the following manner.

The chart for the above question is as follows: