Gerrond, Asof and Lizer are brothers, bound by magic into an experimental military unit. The sorcerer was killed before the brothers saw combat, and the three went their separate ways. However,their lives are still intertwined by the magic that causes only one of them to exist at a time. The one currently "existing" can vanish at will, causing one of the others to reappear elsewhere. While this allows them to protect one another, it prevents them from ever speaking together, and so it is not surprising that they have chosen very different lives since the sorcerer's death.
The Triplet Ghost set was a variation of Geometron's Twin Ghost set.