Kumbhakarna appeared in the Râmâyana in a line of rebirths that started in Brahmâ’s court in heaven (svarga). In that lifetime he had been Vijâya, one of a pair of twin doorkeepers who were cursed for not properly performing their duties.
He was reborn as Hiranyakas´ipu and killed by Vishnu in his Narasimha incarnation (avatâra). Next he was reborn as Kumbhakarna, to be killed by Vishnu in his Râma avatâra. Kumbhakarna was a son of Vis´ravas by his râkshasa (night-wandering demon) wife Keshinî. He was a full brother of Râvana.
The brothers practiced such power austerities (tapas) that the gods became frightened. They had Sarasvatî (goddess of learning) dance on Kumbhakarna’s tongue when he asked Brahmâ for a boon. Kumbhakarna was going to ask for annihilation of the devas (nirdevatvam), but with Sarasvatî dancing on his tongue, he asked for sleep (nidrâvatvam).
So that was what Brahmâ gave him. Kumbhakarna slept for six months and then was only awake for a day. When the war was going poorly for Râvana, Kumbhakarna was awakened, readied for battle with two thousand pots of liquor, and sent against Sugrîva, the great monkey warrior.
Kumbhakarna was able to defeat Sugrîva by pounding him into submission with a giant boulder, and then carried him into Lanka as a prisoner. He returned to the battle and met Râma in single combat. But after a great fight, Râma cut off his head.
Kumbhakarna’s advice to Râvana during various phases of the war showed that he judged his brother’s actions as wrong and yet did his duty as a younger brother. In Brâhmanical orthoprax morality Kumbhakarna had done his duty in that birth.
He was reborn as Dantavaktra, a Dânava king of Karûsha, to be killed by Vishnu in his Krishna avatâra. Then he returned to Vaikuntha, the abode of Vishnu.