In the Star Trek: The Next Generation episode Family, Captain Picard meets his nephew René when he visits his home on Earth. René says,
You're my nephew Jean-Luc.
It is seemingly a joke, though when Picard responds in kind with,
then you must be my uncle René.
René corrects him, saying that it is the other way around.
This dialog always confused me. It seems likely that it is just intending to show René joking around in a way that a young kid would be likely to do. But if this is the case, why did he immediately correct Captain Picard when Picard attempted to continue this joke?
The dialog is referenced again near the end of the episode, when Captain Picard calls René "uncle" again.
I am probably just trying to read more into it than is there; but is there any reasonable explanation for why René first calls Picard his "nephew" and then also corrects him when Picard responds in kind?