Sarah Churchill, Duchess of Marlborough
She was born into the Spencer family as the daughter of Charles Spencer, 3rd Duke of Marlborough (1706–1758), and the Honourable Elizabeth Trevor (d. 1761). Her siblings were George, Charles, and Elizabeth. Her grandmother was the formidable Sarah Churchill, Duchess of Marlborough. She was raised at Langley Park, Buckinghamshire, where she was introduced to art at an early age. Joshua Reynolds, an artist, was a family friend.