The man in the portrait is his son?
Correct.
Not to be argumentative, but your clue and your original riddle don't match.
Your clue, however, says...
Now. The answer to your original riddle is what tpiradam and I said - the man in the painting is the grandson, and the man is the grandfather.
The answer to your "revised" riddle is what Jnelson09 said:
The painting is the man's son, and the man is his father.
Must have been a typo in the book or on my part. Typo on me part. Sorry Ton80.
Here the official answer with explanation.
It is the man's son in the painting. "My father's son" must be the man himself (since he had no brothers or sisters). Therefore "this man's father is my father's son" becomes "this man's father is me". So, the man in the picture is his son.
Deadline: Wednesday, August 20.
Clues: 1
An explorer was captured by a tribe whose chief decided that the man should die. The chief was a very logical man and gave the explorer a choice. The explorer was to make a single statement. If it was true, he would be thrown over a high cliff. If it was false, he would be eaten by lions.
What statement did the clever explorer make that forced the chief to let him go?