"His statement regarding "Terra" and "them" can only mean Ventus and Aqua." Alternatively, "them" could mean Terranort and Lingering Will, as seen in the next shot. Lingering Will is Terra's willpower (and possibly part of his mind? I think I remember Terranort saying as much during their Birth by Sleep confrontation) and Terranort is Terra's body, with his heart imprisoned inside. No matter which one wins, Terra loses.