Son of Tolui and the Kerait princess Sorghaghtani Beki , he was a grandson of Genghis Khan , and the brother of Arik Boke , Mongke and Kublai Khan . Son of Tolui and the Kerait princess Sorghaghtani Beki , he was a grandson of Genghis Khan , and the brother of Arik Boke , MÃ ngke Khan and Kublai Khan .