What is the name of the Animus user's ancestor in Assassin's Creed II?

The Animus user's ancestor in Assassin's Creed II is Ezio Auditore.

Desmond Miles uses the Animus to experience the memories of Ezio, a young Florentine nobleman who becomes an Assassin. Ezio's story begins in Renaissance Italy and spans events in Florence, Venice, Forlì, and other locations.

Ezio is the central protagonist of Assassin's Creed II and its direct follow-ups, Brotherhood and Revelations. His full name is Ezio Auditore da Firenze, meaning Ezio Auditore of Florence. The character is distinct from Altaïr, whose memories Desmond experiences in the first game.

Some players confuse Ezio's role with Desmond's because both appear throughout the narrative. Desmond is the modern-day subject using the Animus; Ezio is the historical ancestor whose life is being relived.