Pointing to a photograph a man said, “He is the son of my father’s only daughter”. How is the man related to photograph?

Uncle

↑ or ↓ ⇒ Upward or downward line shown "generation gap" .

   =    ⇒ Double lines shown "relation b/w Husband & Wife"

   —   ⇒ single line shown "relation between them other than Husband & Wife".

   +   ⇒ Plus sign shown " Male".

   -   ⇒ minus sign shown " Female".

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