During the war Rankin had married Mary Llewellyn in 1942; they would have four children, one son and three daughters. Rankin returned to Cambridge with his wife in 1945 where he became a Faculty Assistant Lecturer.
Sa panahon ng digmaan Rankin had kasal Mary Llewellyn sa 1942; sila ay may apat na bata, isang anak na lalaki at tatlong anak. Rankin ibabalik sa Cambridge sa kanyang asawa sa 1945 kung saan siya ay naging isang Faculty Assistant lektor.