Harcourt was the son of Sir William Vernon Harcourt, son of William Vernon Harcourt, son of the Honourable and Right Reverend Edward Venables-Vernon-Harcourt, son of George Venables-Vernon, 1st Baron Vernon, by his third wife, Martha Harcourt, daughter of Simon Harcourt, son of Simon Harcourt, 1st Viscount Harcourt.