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?

Yes, this is valid.

John has a brother named Joe and a father named Andy.  John and Joe's father Andy has a sister named Ann who happens to be the mother of Joe's wife.  Ann has a husband named Stan who is the father of Joe's wife.

John's wife has a father named Dan.  Dan has a brother named Stan - the same Stan who is married to Ann, the mother of John's brother's wife.

Stan is John's father's sister's husband.
Stan is John's brother's wife's father.
Stan is John's wife's father's brother.

Stan is a blood relative of John's wife and Joe's wife, but is not a blood relative of John or Joe.

Posted by hoodat on 2012-02-04 14:29:25