Answer
Möngke was the first Khagan of the Toluid line. The Toluids were a branch of the Genghisid dynasty, and were descended from Genghis Khan's youngest son, Tolui. Möngke was the fourth son of Tolui, and he succeeded his brother Ögedei as Khagan in 1251. He led the Mongol Empire to its greatest extent, conquering most of Eurasia.