Hi hikaruomega
Ah word maths?..

Ok Man in picture is A and person looking at A?s picture is B

A?s father is B?s fathers son, to simplify A?s father is B
Accordingly A is B?s child, so what is the relationship between the pair?

A?s son is B?s father?s son, A?s is B?s father, which brings us back to A?s son is B....... so A?s is B?s son, because ?this man ? and "my son" have the same father

....