Daddy?

The Answer...

The man is looking at a photo of his son.

Most people say the man is looking at a picture of himself. But the teaser doesn't say, "This man is my father's son." The teaser says, "This man's father is my father's son."

The Question was...

A man is looking at a photo and says, "Brothers and sisters I have none, but this man's father is my father's son." Who is he looking at a photo of?