He was the grandson of Brahmaa's son Pulastya Muni, and the son of Vishravaa Muni and a Raakshas woman Kaikasee (or Keshinee). He had two brothers - Raavan and Vibheeshan and one sister Shoorpanakhaa. He had one step-brother also named Kuber.

Once the three brothers did severe Tap to become the mightiest in the whole world. They did it for 10,000 years. Brahmaa Jee got very pleased with this and appeared before them to bestow them the boon of their choice. First he asked Raavan and bestowed him with whatever he wished for. Then he came to Kumbhkarn. He was very afraid of this Asur, because he used to eat a lot and could eat the whole world if he were awake. So he remembered Saraswatee Jee and asked her help. Saraswatee Jee understood everything, and she entered his body.

Brahmaa Jee came to him and asked him to ask for any boon he wished for. Saraswatee Jee spoke on his behalf - "I wish to sleep my whole life." Brahmaa Jee immediately said - "So be it." and proceeded towards Vibheeshan to bestow him with the boon. Hearing this Raavan got very sad and worried. "What he has done this by asking sleep for his whole life?" Vibheeshan asked for lifelong devotion to Bhagavaan Vishnu. When Brahmaa Jee finished with Vibheeshan, Raavan prayed Brahmaa Jee to reconsider Kumbhkarn's request, saying that he has asked this by mistake. Brahmaa Jee said - "Nothing can be done now. He will have to sleep for his whole life." Raavan somehow managed to ask for one day after every six month sleep for his eating etc.

All came down the mountain on which they were doing this Tap. One day the Sleep came to Kumbhkarn and said to him - "I have come to you as you wished for." Kumbhkarn said to Raavan - "Brother, Build me a great palace, I wish to sleep." Raavan asked his people to build a magnificent palace for him and he went there to sleep in it. Now he slept for six months and woke up for one day to eat. He ate so much that during that he ate several buffaloes, drank several pitchers of liquor; and then slept again after eating.

If he had to be awaken in between it took several days to wake him up. People had to beat many drums at the top of their force and speed. Raavan had to keep his food ready to eat. So when Raam-Raavan war occurred, Raavan had to wake him up like this. When he came to know about what Raavan had done (abducting Seetaa Jee and fighting with Raam and Lakshman) he got annoyed with him and explained him to return Seetaa to Raam as He was Bhagavaan Himself. Raavan threatened to kill him, so he thought that it was better to be killed by the hands of Raam so he went to fight with Him. There Raam killed him and he went to Swarg.