John Snoggs: "… Listen again. You happen to be my father's brother in-law, my brother's father in-law and also my father's in-law brother.
You see, my father was…"

Abridged from Dudeney's " Amusements in Mathematics" (1917)

You might be surprised : what follows is a logical, coherent explanation.
Can you provide one?

Let 'You' be Y, and 'my father' be X.

Step 1: X marries the unrelated female Z, with issue B, who subsequently marries Y's daughter. (Y is B's father in law). Z dies.

Step 2: X marries Y's sister, with issue Snoggs. (Y is X's brother-in-law and X is Snogg's father.)

Step 3: X and Y each have one surviving parent; these parents marry; X and Y are hence step-brothers.

 

Posted by broll on 2011-09-26 21:42:08