What’s the answer to the riddle, “That man’s father is my father’s son”?

Dear Cecil: This riddle has been bugging for years now. A man is standing in front of a judge waiting for sentencing, when all of a sudden he excitedly gestures toward a picture of a gentleman hanging on the wall above the judge’s head. The prisoner exclaims, “That man’s father is my father’s son!” Who is the man in the picture? Please solve this. G.G., Chicago

Cecil replies:

I’d love to, but unfortunately you goofed up the joke. Usually it goes, “Brothers and sisters have I none, but that man’s father is my father’s son.” Rhymes, you see. Rash and impetuous persons are often inclined to say that the guy in the picture is the speaker himself. However, those who have had their minds toughened by regular exposure to the Straight Dope will see at once that the guy in the picture is the speaker’s son. The way you tell it, though, the guy could be either the speaker’s son or his nephew. (You may want to ponder this for a while.) Take it from me, sport–humor is no business for amateurs.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.