Who was Alan Turing's older brother?

Alan Turing’s older brother was John Turing, formally John Ferrier Turing.

John was born before Alan and was the elder of the two sons of Julius Mathison Turing and Ethel Sara Turing. Because their father served in the Indian Civil Service, the family had connections with British India, but Alan and John were largely raised in Britain while their parents travelled between India and England.

John later became the father of Sir John Dermot Turing, making Dermot Alan Turing’s nephew. The family connection is sometimes obscured because sources may shorten John Ferrier Turing’s name to John Turing, but “John Turing” is the canonical short answer to this quiz question.

John also supported Alan during the difficult legal proceedings that followed Alan’s 1952 conviction for homosexual acts. Alan’s family history is separate from his public scientific legacy: John did not share Alan’s fame as a mathematician, cryptanalyst and computer pioneer, but he remained an important figure in biographies and family memoirs about him.