Jack was a space mission commanding officer in 2210. He was a relative of Harry Kim, who referred to him as an uncle.
Harry once told the story of Uncle Jack to his crewmates of Voyager's senior staff. He recounted that Jack had commanded a mission to Beta Capricus, a deep-space mission at that time. The journey took six months, his uncle piloting the spacecraft the entire time, as the rest of the personnel were in stasis. Upon arrival, it turned out that Beta Capricus did not exist anymore, its detectable emissions were nothing more than an electromagnetic echo from the distant past. Jack did not wake his crew because there was nothing to do or see, and returned to the Sol system. When they arrived six months later, Jack brought the crew out of stasis and they wondered why they had not left Earth's orbit. (VOY: "11:59")