Constellation:

Capricornus

Character:

He is a Syrian Assassin whose birthday is the 11th of January 1165 and who lived during the third Crusade. The name ibn La-Ahad means "Son of no one" in Arabic, although the accuracy of the translation is heavily questioned. Additionally, Ben Reeves of Game Informer adds that the "name of the top assassin is also the name of a star in the constellation Aquila - Aquila being another name meaning eagle. Not coincidentally Ezio is the Italian form of a Greek name that also means "eagle". Altair is an ancestor of Desmond Miles. 

Source from Wikipeida