Nice one Maarten
This riddle, one of the world's oldest, is still good for starting arguments. A man is looking at a portrait. "Whose picture is that?" someone asks, and the man replies: "Brothers and sisters have I none, but that man's father is my father's son." At whose picture is the man looking?
--------------------------------------------------------------------------------
The portrait is of the man's son. Many people mistakenly argue that the man is looking at a picture of himself. If he had said, "... that man is my father's son." then this solution would be correct, but he said, "... that man's father is my father's son." One way out of the confusion is to substitute the word "me" for the more cumbersome phrase "my father's son." Then the statement becomes, "that man's father is me."