Pointing to a man in the photograph a woman said, "He is the son of my paternal grandmother's only son. How is the man related to the woman?

Brother

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: