John Spencer-Churchill was born on 2 June 1822, eldest son of the 6th Duke and his first wife, Jane. He was educated at Eton and Oriel College, University of Oxford and in 1843 married Lady Frances Vane, having eleven children.

As Lord Blandford (the title of the Duke of Marlborough's heir), he became MP for the local constituency, Woodstock [Oxfordshire], from 1844-45, then 1847-57. Following his succession to the dukedom in July 1857, he moved to the House of Lords, giving up his constituency and becoming Lord Lieutenant of Oxfordshire (1857-83). His other positions included: High Steward of Woodstock and Lord Steward of the Household (1866-67); Lord President of the Council (1867-68); Lord Lieutenant of Ireland (1876-80). He died on 5 July 1883.

His third son, Lord Randolph Henry Spencer-Churchill, was born on 13 February 1849. He was educated at Oxford and in 1874 married Jennie Jerome, having two sons, Winston and John Churchill. Lord Randolph's political career included: MP for Woodstock (1874-85) and for Paddington, London (1885-95); Secretary of State for India (1885-86); Chancellor of the Exchequer (1886). He died on 24 January 1895.