Can they go to court and get it back?

The money was borrowed sometime in 2000. It was from and Uncle to a Nephew. He borrowed $16,500 and never paid a cent!

Can the Uncle try and get his money back or is it too late?

Asuming that there is no written contract for this loan - it'll be difficult unless there are witnesses to the oral contract. The fact that the uncle has waited 10 years implies that this was actually a gift, not a loan. Does the uncle have any written documentation that he tried to get the nephew to repay over the years?

I believe he does. The reason he waited was because he was not hurting for money and knows that his nephew was going through a divorce and didn't want to add to it! In the divorce agreement he signed stating he takes the loan from his Uncle while the Former wife took the debt of her mother.