Looking at the picture of a man, Geeta said, "His brother's father is the only son of my grandmother." How is Geeta related to the man in the picture?

Sister

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: