Quote Originally Posted by masamune1600
In addition to General Leo, Banon, Biggs, and Wedge, a Ghost (or Ghosts, if you use Posess and then pick up another) briefly joins your party on the Phantom Train. Also, at the very beginning, a number of moogles aid Terra in her escape. They are used in parties, and qualify under the question.
Very good. But you missed one.

Remember, I said are under your control, not necessarily in battles. Maybe not a "party member" per se, and maybe not in a battle, but still under your control for a time.