Churchill was born on November 30, 1874, into the aristocratic family of the Dukes of Marlborough, a branch of the Spencer family, Winston Leonard Spencer-Churchill, like his father, used the surname Churchill in public life.

His ancestor George Spencer had changed his surname to Spencer-Churchill in 1817 when he became Duke of Marlborough, to highlight his descent from John Churchill, 1st Duke of Marlborough. Winston's father, Lord Randolph Churchill, the third son of John Spencer-Churchill, 7th Duke of Marlborough, was a politician; and his mother, Lady Randolph Churchill (née Jennie Jerome) was the daughter of American millionaire Leonard Jerome.

Winston Churchill's Family Tree