Nardo claims to be the great great great grandson of Leonardo da Vinci however there is very little historical evidence that da Vinci sired any children in his lifetime and very strong evidence that he was in fact homosexual.
When Jack, Emilia, and Blackbeard are up in the hot air balloon, Jack looks over at the boat containing the "Founding Fathers and Sons." We see George Washington dancing (Jack makes a crack at that). The show takes place in 1801. Washington died in 1799, two years before the fact. Blackbeard was killed in combat 83 years before.