Douglas Gresham was born in New York City, the son of writers William Lindsay Gresham and Joy Davidman. William Gresham was the author of Nightmare Alley, the classic of American noir literature, while Joy Davidman was best known for her book Smoke on the Mountain, about the Ten Commandments. The couple were divorced in 1954, and Joy moved to England with her two sons.
Gresham’s mother had become friends with C. S. Lewis through correspondence, and the friendship blossomed, eventually leading to marriage in 1956. Gresham’s mother died of cancer in 1960, and Lewis continued to raise Douglas and his elder brother David. (Lewis had adopted the boys when he married, and The Horse and His Boy is dedicated to them both). At Lewis’ death in 1963, his estate went to his brother Major Warren Hamilton Lewis, a renowned scholar of French history. The Major in turn passed the estate to Douglas and David ten years later. Douglas Gresham acknowledged in a 15 November 2005 interview on NPR that he and his brother are estranged, although in a 4 December 2005 interview he did say that they are in email contact. Douglas Gresham is a Christian, as were Lewis and his mother, while David returned to the Orthodox Judaism of their mother’s ancestors while still a child in Lewis’s home. Lewis made an effort to find kosher food for him.
Gresham hosted Focus on the Family‘s radio adaptations of his stepfather’s most famous works, and his interest in media versions thereof was later shown again when he was named co-producer for the series of theatrical films adaptations of The Chronicles of Narnia; he also made a cameo in the first installment as a radio newscaster, the second as a “Telmarine crier” and the third as a slaver.