Herbert was born at Ashtead Lodge, Ashtead, Surrey on 24 September 1890. His father, Patrick Herbert Coghlan Herbert (1849-1915), was a civil servant (assistant secretary of the Judicial and Public Department) in the India Office, of Irish origin, and his mother, Beatrice Eugenie (née Selwyn), was the daughter of Sir Charles Jasper Selwyn, a Lord Justice of Appeal. He had two younger brothers, both of whom died in battle- Owen william Eugene, 2nd Lieutenant, Royal Field Artillery, killed at Mons in 1914, and Sidney Jasper, Captain R.N., killed 1941 aboard the H.M.S. Hood. His mother died of tuberculosis when he was eight years old, shortly before he left to attend The Grange in Folkestone, a preparatory school.