On 8 November 1766, Portland married Lady Dorothy Cavendish, a daughter of William Cavendish, 4th Duke of Devonshire and Charlotte Boyle. They were parents of six children: William Bentinck, 4th Duke of Portland (24 June 1768 – 27 March 1854). Lord William Henry Cavendish-Bentinck (14 September 1774 – 17 June 1839).
Cavendish-Bentinck was the elder son of Lieutenant Colonel Lord Charles Bentinck and Anne Wellesley, formerly Lady Abdy. His paternal grandparents were William Cavendish-Bentinck, 3rd Duke of Portland , Prime Minister of Great Britain , and Dorothy Cavendish, a daughter of William Cavendish, 4th Duke of Devonshire .
General Info. The list below shows descent from William the Conqueror (see Descendants of William I of England for another list). Many of the people have more than one path to William, but this is mostly just showing one (ideally the shortest path).