Pointing to a person seen in the photograph, Preeti said, "He is the son of the only daughter of my husband's father-in-law, Gopal." How is the person seen in the picture related to Preeti?

Let's break down the relation step-by-step from Preeti's perspective:"my husband's father-in-law" $\to$ Preeti's husband's father-in-law is Preeti's own father (Gopal)."the only daughter of my husband's father-in-law" $\to$ The only daughter of Preeti's father is Preeti herself."He is the son of [Preeti herself]" $\to$ The person is Preeti's son.Therefore, the person in the photograph is Preeti's Son.