Yes, plenty of honest mistakes, and old family myths. Plenty of deliberate mistakes, too, handed down from earlier times.
Shakespeare’s father bought himself a coat of arms, after he had made some money. That was not uncommon among up-and-coming Brits in those days. The beer barons in the time of Queen Victoria are another famous instance.
Napoleon's father also made a ton of money somewhere other than Corsica ~ I suspect that was in the fur trade in the then Western frontier of New York colony ~ after the Napoleonic wars, virtually all of Napoleon's relatives ended up in Upstate right where the furtrade activities took place. Many of their descendants continue to live in the area. (Otsego_.