He was the son of George Nugent Temple Grenville, 3rd Earl Temple, who was the son of Prime Minister George Grenville, and who had been created "Marquess of Buckingham" in the peerage of Great Britain in 1784. The 1st Marquess of Buckingham had married Lady Mary Nugent, daughter of Robert Nugent, 1st Earl Nugent. Mary was in 1800 created Baroness Nugent in her own right in the Peerage of Ireland, with remainder to her second son George (see the Baron Nugent). In 1788 Lord Buckingham also succeeded his father-in-law as second Earl Nugent according to a special remainder in the letters patent, and at the same time assumed by Royal licence the additional surname of Nugent.