during the war, Ravana went into battle and was humiliated by Rama and his army. He decided he needed the help of his brother Kumbhakarna, who was awakened with great difficulty. He woke up only after one thousand elephants walked over him(Rāmāyaṇa 6.48.47).
When he was informed of the circumstances of Ravana’s war with Rama, he tried to convince Ravana that what he was doing was wrong. However, he chose to fight in the battle due to his loyalty to his brother. After becoming drunk, Kumbhakarna went into battle and devastated Rama’s army. He knocked Sugriva unconscious, took him prisoner, but was ultimately killed by Rama. When Ravana heard of his brother’s death, he fainted and proclaimed that he was truly doomed.
Kumbhakarna had two sons, Kumbha and Nikumbha, from his wife Vajramala who too fought in the war against Rama and were killed. He had another son named Bhimasura from his another wife Karkati who was the princess of sayadri, but later when she heard about his husband’s death than to take avenge from Lord Rama he ordered her son to harsh penance of Lord Bramha and take a boon to remain invincible but later Bhimasura was killed by Lord Shiva.