Stephen John Keynes (19 October 1927 – 13 August 2017) was a great-grandson of Charles Darwin, and chairman of the Charles Darwin Trust. He was educated at The Hall School, Hampstead, Oundle School, and King's College, Cambridge, where he was an Open Scholar. Keynes was the fourth son of Geoffrey Keynes and his wife Margaret Darwin, daughter of Sir George Darwin; he was also a nephew of the economist John Maynard Keynes. His brothers were Richard, Quentin and Milo. In 1955 he married Mary Cecilia Knatchbull-Hugessen, daughter of the Canadian senator Adrian Knatchbull-Hugessen. They had the following children: Keynes was a Fellow of the Linnean Society of London and a member of the Roxburghe Club.