In Assassin's Creed II, Ezio Auditore's sister is named Claudia.
Claudia is one of Ezio's closest surviving family members after the Auditore family is targeted in Florence. At the start of the game, Ezio's father Giovanni and brothers Federico and Petruccio are executed, forcing Ezio to leave Florence and begin a life connected to the Assassins.
Claudia later becomes an important figure in the story surrounding the Assassin brotherhood. In Assassin's Creed: Brotherhood, she manages the finances and organization of the rebuilt Assassin network in Rome, and the player can help her develop those skills.
Claudia is sometimes confused with Cristina Vespucci, Ezio's former romantic interest, because both women are prominent in Ezio's personal story. They are separate characters: Cristina is associated mainly with Ezio's memories and relationships, while Claudia is his sister and a member of the Auditore family.