Lord Randolph Churchill

Lord Randolph Henry Spencer-Churchill (13 February 1849 – 24 January 1895) was Winston Churchill's father. He was a son of the 7th Duke of Marlborough. 
He was a leading British Tory politician. Churchill was a Tory radical who coined the term "One-nation conservatism". 
He inspired a generation of party managers and created the National Union of the Conservative Party. He broke new ground in modern budgetary presentations. He got admiration and criticism from across the political spectrum. His disloyalty to Lord Salisbury was the beginning of the end of what might have been a glittering career. His elder son, Winston, wrote a biography of him in 1906.
Medical condition and early death.
Churchill died early, suffering from a disease. That disease was either syphilis or a brain tumour or even multiple sclerosis. 
It is definitely the case that he was treated for syphilis, and it has been suggested that he was suffering from symptoms of the mercury-based medication. The Churchills' family doctor in the 1880s had written about syphilis. He referred Randolph to the specialist Thomas Buzzard, and continued to prescribe potassium iodide and mercury.