Since Amitodana was the brother of Suddhodana, king of the Sakyas in Kapilavastu, Anuruddha was cousin to Siddhartha, (Gautama Buddha).
Gautama Buddha returned to his home town two years after his enlightenment, preaching his ideas to the Sakyan kingdom.
Together with his 3 cousins Bhaddiya, Ananda, and Devadatta and their servant Upali, became ordained by the Buddha at the Anupiya Mango Grove.
In many texts, even when many distinguished monks were present, Anuruddha is often the recipient of the Buddha's questions, and answers on behalf of the sangha.
He was foremost in consoling the monks and admonishing their future course of action, reminding them of the Buddha's decree to follow the Dharma.
As the Buddha was reclining and going through the jhanas, Ananda said to Anuruddha: "The Exalted One has attained final Nibbana, Venerable Sir."