The empire began to split due to wars over succession, as the grandchildren of Genghis Khan disputed whether the royal line should follow from his son and initial heir Ögedei, or one of his other sons such as Tolui, Chagatai, or Jochi. After Möngke Khan died, rival "kurultai" councils simultaneously elected different successors, the brothers Ariq Böke and Kublai Khan, who then not only fought each other in the Toluid Civil War, but also dealt with challenges from descendants of other sons of Genghis. Kublai successfully took power, but civil war ensued as Kublai sought unsuccessfully to regain control of the Chagatayid and Ögedeid families.