| Henrietta Countess|| December 9, 1755|
| Margaret Bentinck, Duchess of Portland|
William Cavendish-Bentinck, 3rd Duke of Portland, Lord Edward Bentinck
Lord William Bentinck, Lord Charles Bentinck, William Bentinck, 4th Duke of Portland
Edward Harley - 2nd Earl of Ox, Margaret Bentinck - Duchess, William Cavendish‑Bentinck - 3rd Duke, Robert Harley - 1st Earl of Ox
Henrietta Harley, Countess of Oxford and Countess Mortimer Wikipedia
Henrietta Harley (nee Holles), Countess of Oxford and Countess Mortimer (11 February 1694 – 9 December 1755) was an English noblewoman, the only child and heiress of John Holles, 1st Duke of Newcastle and his wife, the former Lady Margaret Cavendish, daughter of Henry Cavendish, 2nd Duke of Newcastle-upon-Tyne.
Her hand was sought in marriage even in her youth, as a means of alliance with her powerful father, by the Intendant of the Court of a Count of the Holy Roman Empire in December 1703, the Elector of Hanover's son in June 1706, the Duke of Somerset's son Lord Hertford in 1707-11, Count Nassau in 1709, and finally Lord Danby (grandson of Thomas Osborne, 1st Duke of Leeds) in 1711, before her father settled on Edward Harley, 2nd Earl of Oxford and Earl Mortimer. They were married on 31 August 1713, at Wimpole. They had two children. Their son, Henry Cavendish Harley, Lord Harley, lived only four days. Their only child to attain maturity was Margaret (1715–1785), and so whilst Margaret inherited most of the combined Holles-Harley fortunes on her parents' deaths, the title of Earl of Oxford and Earl Mortimer passed to Edward's cousin (also Edward).