Montgomery was born in Kennington, London, in 1887. He was the fourth child of nine. His parents were The Reverend Henry Hutchinson Montgomery, an Anglo-Irish Anglican priest, and Maud Montgomery (née Farrar). Henry Montgomery was the second son of the noted British Indian Empire official, Sir Robert Montgomery, who died a month after Bernard's birth. Bernard's mother Maud was the daughter of the well-known preacher Frederic William Farrar, and was eighteen years younger than her husband. The loveless environment made Bernard something of a bully, as he himself later recalled "I was a dreadful little boy. I don't suppose anybody would put up with my sort of behaviour these days."