Nov 26 2010, 5:13pm
that the word 'Uncle' was being used as an affectionate term, not a literal one. Some children in real life refer to their parents' close friends as 'aunts' or 'uncles'. It wouldn't be much of a stretch for the young Frodo to grow up knowing his father's ageing cousin as 'Uncle Bilbo'. Or perhaps he only started calling him that when he was adopted by him.
I think the non-literal uncle/nephew relationship is even mentioned at some point in the books.
(This post was edited by Flagg on Nov 26 2010, 5:13pm)