Son of William (d. 1713), Earl of Kingston, and Rachel Baynton. Married (1769) to Elizabeth Chudleigh (1720-1788). He inherited the title of Duke of Kingston from his grandfather on March 5, 1726. In 1741 he became a Knight of the Garter, and in 1745 he distinguished himself by raising a cavalry regiment to fight the Jacobite rebels at Culloden. He was the bearer of St. Edward's staff at the coronation of King George III in 1761, and in 1763 he was appointed Lord Lieutenant of Nottinghamshire. In 1772 he was promoted to General of the Army, but he died a little over a year later, at Bath, on September 23, 1773.
On December 7, 1762, Boswell went to a breakfast and concert at Lord Eglinton's in London, which was also attended by Pierrepoint (the Duke of Kingston) and others.