Born at Kensington, Bentinck was the elder son of Lieutenant Colonel
Lord Charles Bentinck and of
Anne Wellesley, formerly Lady Abdy. He had a younger brother, Arthur Cavendish Bentinck, and two sisters, Anne and Emily. He was frequently addressed as William or William-Charles to distinguish him from his father. Later in life, he presented his name as William Charles Cavendish Bentinck, resulting in his "W. C. C. Bentinck" signature. He rarely used the
double-barreled Cavendish-Bentinck surname. Bentinck's 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, another prime minister, by his marriage to
Lady Charlotte Boyle, a daughter of
Richard Boyle, 3rd Earl of Burlington. After taking his degree, Bentinck confirmed his plan of becoming a
Church of England clergyman and was appointed as Vicar of
Husborne Crawley, Bedfordshire, a
benefice in the gift of
Francis Russell, 7th Duke of Bedford. On 23 November 1849, the Duke also appointed him as vicar of
Ridgmont, Bedfordshire. In both parishes, he was known as William Charles Cavendish Bentinck. The likelihood of Bentinck becoming Duke of Portland increased when his uncle
William Bentinck, 4th Duke of Portland died on 27 March 1854, with all four of his sons then dead or unmarried. The eldest,
William, Marquess of Titchfield, had died in 1824, and
Lord George in 1848. The eccentric
Lord William (who succeeded his father as the 5th Duke of Portland) and the youngest son,
Lord Henry, both remained unmarried. Bentinck himself was the next heir after Lord Henry, but he was also childless at the time: his wife Sinetta had died at Ampthill on 19 February 1850, of
mesentery, leaving Bentinck a widower with no surviving children. Bentinck died on 17 August 1865, aged 47, at Ridgmont, and was buried at
Croxton, Cambridgeshire. His cousin Lord Henry William died in 1870, and the 5th Duke followed on 6 December 1879. Thus, the next Duke was Bentinck's nephew
William Cavendish-Bentinck, a son of his younger brother Lt.-General Arthur Cavendish Bentinck, who had died in 1877. == Marriages ==