Darim Ibn-La'Ahad

Darim Ibn-La'Ahad (born 1193) was a member of the Assassin Order and the first son of Altaïr Ibn-La'Ahad and Maria Thorpe. Later he became the brother to Sef Ibn-La'Ahad, Altaïr and Maria's second son. At a later age Darim left with his father and mother for Mongolia to assassinate Genghis Khan. After succesfully assassinating Genghis Khan and the death of his brother and mother, he lived for a time with his father, sister-in-law and his nephews in Alamut. He was driven away by his father's remorse and state of depression and left for England and France to warn the Assassins there about the rising Mongol threat.

Source

 * Assassin's Creed: The Secret Crusade