What was the name of C.S. Lewis’s brother and longtime collaborator?

C.S. Lewis’s brother and longtime collaborator was Warren Lewis.

Warren Hamilton Lewis, usually called Warnie, was born in 1895, three years before his younger brother. He served in the British Army during the First World War and later worked as a historian. The brothers shared a home for much of their adult lives, including The Kilns near Oxford.

Warren kept extensive diaries that document the Lewis household, literary friendships, and daily events. After C.S. Lewis’s death, these records became an important source for biographers and readers studying his life. Warren also helped manage practical matters connected with his brother’s writing.

Warren is sometimes confused with Albert James Lewis, their father. Albert was a solicitor and the boys’ father; Warren was the elder brother. The brothers’ close relationship also influenced the household portrayed in biographies of Lewis and in accounts of the Inklings.