Question: Who is John Kemys Spencer-Churchill's paternal grandfather?
Answer: George Spencer-Churchill, 5th Duke of Marlborough

Lord Charles Spencer-Churchill (3 December 1794 – 28 April 1840) was a British army officer and politician. He was the second son of George Spencer-Churchill, 5th Duke of Marlborough and Lady Susan Stewart, daughter of John Stewart, 7th Earl of Galloway. John Kemys George Thomas Spencer-Churchill (27 December 1835 – 9 August 1913) was an administrator in the British colonial service serving as Governor of Montserrat and Commissioner of St Kitts and Nevis