What was the name of C.S. Lewis’s brother and frequent biographer?

C.S. Lewis’s brother and frequent biographer was Warren Lewis.

Warren Hamilton Lewis was C.S. Lewis’s older brother, born in 1895. He served in the British Army and later became a historian. Warren kept extensive diaries, many of which document his brother’s life, friendships, work, and religious development.

The brothers shared a home for many years after returning to Oxford. Warren’s records became an important source for later biographical studies of C.S. Lewis, especially because they preserve details unavailable from Lewis’s published works.

Warren is sometimes confused with Albert James Lewis, their father, or with Lewis’s friend Owen Barfield. Warren was the sibling who lived with Lewis and recorded much of the author’s adult life in diaries and memoir material.