What happened to Genghis Khan's empire after his death

Genghis Khan named his third son as heir. This resulted in a bitter fight between the siblings. The empire under the third son continued to expand both east and west.

when he died, his empire was expanded by his son.

Explanation:

Genghis Khan died in 1227. At the time of his death the Mongol empire extended from Caspian Sea in the west to the Pacific in the east. After his death, Genghis Khan was succeeded by his son Ogedei. Ogedei further expanded the empire on all sides