In Assassin's Creed Brotherhood, the protagonist Ezio's surname is Auditore.
Ezio Auditore da Firenze returns as the playable Assassin in Brotherhood, which continues his story after Assassin's Creed II. The game is set mainly in Rome, where Ezio works to weaken the Borgia family's control and rebuild the local Assassin Brotherhood. His family name identifies his Florentine origins and links him to the events that began in the previous game.
Brotherhood is not a separate protagonist story in the way that later numbered games often are. Instead, it is the middle chapter of Ezio's trilogy, between Assassin's Creed II and Assassin's Creed Revelations. The game also introduced a system allowing Ezio to recruit and train new Assassins.
The surname is sometimes shortened in casual discussion, but the canonical full name is Ezio Auditore da Firenze. Auditore should not be confused with Frye, the surname of Jacob and Evie in Assassin's Creed Syndicate, or Kenway, used by major characters in the colonial-era games.