They're my favorite too, but I can tell you that there is categorically no evidence that anyone like Ezio or the Auditore family existed at all, and the games get a while lot of 15th century finance wrong (Ezio's father's career in the Medici bank is improbable). There's also a whole bunch of improbable backstory involving about Altair's descendants that even involves Marco Polo which makes for good trivia, but is historically inaccurate.

I don't have any sources, because I can't disprove that someone named Ezio Auditore did exist.