Lieutenant Gregory Bergan was a 24th century Starfleet officer who served aboard the USS Melbourne when it fought the Borg at the Battle of Wolf 359 in 2367.
In 2375, when the USS Voyager encountered a Borg vinculum, Seven of Nine began to experience the personalities of various assimilated individuals, including that of Bergan's mother. According to Seven, he was supposed to have met up with her at Wolf 359, but Starfleet had sent out a warning that the Borg were attacking that sector. Bergan's mother was caught in the battle and the starship she was on was badly damaged, forcing the crew to leave in escape pods. Bergan's mother was assimilated by the Borg shortly thereafter. (VOY: "Infinite Regress")
He may have been lost in the battle.