Who is Devadatta?
Source: http://www.buddhanet.net/e-learning/buddhism/lifebuddha/2_5lbud.htm
Devadatta, the Buddha's Enemy
Devadatta was the son of King Suppabuddha and his wife Pamita, who was an aunt of the Buddha. Devadatta's sister was Yasodhara, making him both a cousin and brother-in-law of the Buddha. Together with Ananda and other Sakyan princes, he entered the order of monks in the early part of the Buddha's ministry, but was unable to attain any stage of sainthood and so worked hard for the worldly psychic powers.
In his early days, he was a good monk known for his grace and psychic powers. Later he became conceited with worldly gain and fame. As his ill-will and jealousy towards the Buddha increased, he became the greatest personal enemy of the Buddha.
One day in a large assembly, which included kings and princes, Devadatta approached the Buddha and asked him to make him the leader of the Sangha. Since he was not capable and worthy enough, the Buddha turned down this request. Devadatta became very angry as a result and vowed to take revenge on the Buddha.
