The Pazzi family becomes Ezio Auditore’s main enemy in Florence in Assassin's Creed II.
The game adapts the Pazzi conspiracy of 1478, a real attempt by members of the Pazzi family and their allies to overthrow the Medici family’s power in Florence. In the fictionalized story, the conspiracy is connected to the Templars and to the murder of Ezio’s father and brothers. Ezio pursues the conspirators while building his role within the Assassin Brotherhood.
The Medici family is an ally and major political force, not Ezio’s principal enemy in this storyline. The Borgias become especially important in later games, while the Sforza family is another Renaissance dynasty represented in the series. These names are historically related but refer to different factions or games.