Frederick Cavendish-Bentinck British soldier and Member of Parliament (1781-1828) (1781–1828) Parents Dorothy Bentinck, Duchess of Portland William Cavendish-Bentinck, 3rd Duke of Portland Children George Cavendish-Bentinck Siblings Lord Charles Bentinck William Bentinck, 4th Duke of Portland Lord William Bentinck Charlotte Cavendish-Bentinck Partners Mary Lowther