Oneir was born to unknown parents. He was on a train alongside Christopher and Fenning. When he was young, he accidentally killed his friend Christopher Chant by hitting him on the head with a cricket bat. He also gave Christopher books from Twelve-A in response to the Living Asheth's request.
Oneir married an unnamed woman, and became the father of Carol Oneir and lived in Surrey. When she lost her dreaming ability, Oneir went fishing. When the house had newspaper reporters outside, Oneir created an excuse, saying that his daughter was tired and that they were taking her to Switzerland to rest. In reality, he had arranged an appointment with Christopher Chant while Christopher was on holiday in the south of France. He believed Carol when she explained that her main characters had gone on strike.