Biography
Robert Spencer was born on 24 October 1701 the second, but eldest surviving son of Charles Spencer, 3rd Earl of Sunderland, and his second wife, Lady Anne Churchill, daughter of John Churchill, 1st Duke of Marlborough, and his wife Sarah Jennings.
He was known by the courtesy title of Lord Spencer from 1702 to 19 April 1722 when he succeeded his father as 4th Earl of Sunderland.
He died of a fever at Paris on 15 September 1729, and was buried at Brington on 7 October 1729. He was succeeded by his younger brother Charles Spencer, as 5th Earl of Sunderland, who eventually succeeded as 3rd Duke of Marlborough.
Sources
Cokayne, George Edward, The Complete Peerage: or a history of the House of Lords and all its members from the earliest times, 2nd ed., vol. 12 (part 1), revised & edited by Geoffrey H. White. London: St Catherine Press, 1953. Published in electronic form by ABC Publications, London. (page 489)