math teaser, kinda tough

[setzf]

i just realised something...i dont think this question is well formulated and i think the only way to solve it is to add an assumption, ie:
Age(John)>Age(Art) does not imply Art is not John's uncle (in reality) since uncles CAN be younger than nephews.
So to solve the problem i think (but am not sure) that you MUST assume that uncles cannot be younger than nephews

thoughts?