Pointing out a picture of old man, Deepak said, "His son is my son's uncle." How is the old man related to Deepak?

Father

Note:

↑ 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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Old man is father of Deepak.