Simplify the following text for a Grade 9 native English-speaking person.
Original: 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 .
Simplified: 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 .