 His father Count Robert Charles Bentinck (1875–1932) died when Bentinck was only twelve.He was a descendant of William Bentinck, 1st Count Bentinck (1704–1774), younger son of William Bentinck, 1st Earl of Portland, and half-brother of Henry Bentinck, 1st Duke of Portland.His mother Lady Norah Ida Emily Noel, eldest daughter of Charles William Francis Noel, 3rd Earl of Gainsborough, died when he was 19.