His father, a British barrister, Conservative politician, and cricketer who was also a member of parliament from 1859 to 1891, was the only son of Major-General Lord Frederick Cavendish-Bentinck (1781–1828), who was the fourth son of Prime Minister William Cavendish-Bentinck, 3rd Duke of Portland (1738–1809), and brother to William Bentinck, 4th Duke of Portland (1768–1854).
Cavendish-Bentinck was private secretary to Henry Holland, 1st Viscount Knutsford (1825–1914), at the Colonial Office and to Frederick Stanley, 16th Earl of Derby (1841–1908) at the Board of Trade.
[6] In the general election of 1885, Cavendish-Bentinck ran for a seat in parliament during the but was unsuccessful, losing to David James Jenkins, a Liberal who received 52.3% of the vote.
[9][11] Together, they had: In 1899, Louisa Matilda Livingston, a cousin of Cavendish-Bentinck's wife, who was married to Elbridge T. Gerry, the grandson of grandson of US Vice-president Elbridge Gerry, gave a reception and dance in honour of their eldest daughter, Mary, in advance of her presentation the following spring at the Court of St. James and subsequent debut in London Society.
[1][18] In 1914, his widow built a family mausoleum in the Churchyard of St Giles in Hertfordshire, designed by Robert Weir Schultz.