Answer to Puzzle #50: Brothers And Sisters I Have None

50. A man is looking at a photograph of someone. His friend asks who it is.
The man replies, 'Brothers and sisters, I have none. But that man's father is my father's son'.
Who is in the photograph?

Another very popular puzzle, which I think it's about time we included. Perhaps we can find a better way of explaining it:

Before reading the answer can I interest you in a clue?

Let's break the puzzle down in to smaller pieces and then put them together and see what we've got. 'My father's son.' We'll draw a diagram from the perspective of the person speaking.
family tree diagram for my fathers son
My Father's son is my sibling.

'That man's Father' appears in our diagram already, we know him as My Father's son. They are the same remember that man's father is my father's son'
family tree diagram for that mans father
'Brothers And Sisters I Have None' - thus far we have identified My Father's Son and Me as separate people. But if I have no brothers or sisters then my father's son can only be me.
family tree diagram for that mans father is my fathers son
Or just...
family tree diagram for brothers and sisters i have none that mans father is my fathers son
To clarify 'That Man' is my son. If I have no brothers and sisters then my father's son can only be me. Which means I (me) am that man's father.

As you'd expect both AI's got this correct. It is, after all, a classic.

If you're curious what Bard made of this puzzle...

If you're curious what ChatGPT made of this puzzle...

© Nigel Coldwell 2004 -  – The questions on this site may be reproduced without further permission, I do not claim copyright over them. The answers are mine and may not be reproduced without my expressed prior consent. Please inquire using the link at the top of the page. Secure version of this page.

PayPal - The safer, easier way to pay online.
I always think it's arrogant to add a donate button, but it has been requested. If I help you get a job though, you could buy me a pint! - nigel

This Website Uses Cookies

To increase the functionality of the site. The cookies I apply do not uniquely identify you, by continuing to use this site you agree to let me place a cookie. I also have advert and analytics providers, my advertising provider (Google,) does provide personalised adverts unless you specify otherwise, with them. For more information click here.x