Kadar Al-Sayf

Kadar Al-Sayf is a novice Assassin and a loyal Sunni Muslim, the younger brother of Malik. From Kadar's words in Solomon's Temple, it is evident that he admires Altaïr's skill and rank.

Kadar was killed near the beginning of Assassin's Creed, in Solomon's Temple, during the first confrontation with Robert de Sable. Malik, already embittered toward Altaïr for his breaking of the Tenets, is infuriated by his brother's death. He believes that without Altaïr's arrogant actions, Kadar would have lived, and he (Malik) would not have lost his arm.

Speculation

It was speculated that he was not killed immediately, but instead taken hostage, being the hostage Robert de Sable had executed outside the Assassins' fortress. However, the hostage is not wearing the robes of a novice that Kadar was wearing in the temple. Malik himself had said that Kadar died at Solomon's Temple.

Assassin's Creed: Altaïr's Chronicles

There is another assassin named Kadar that appeared in Assassin's Creed: Altaïr's Chronicles prequel.