>>531533073
If Gremory was based: Dual character with both on the field, where one leads and one follows. You can switch between them, and each skill is essentially two skills because it depends on which twin is leading.
If Gremory was competent enough: Only one twin on the field, and can switch, which teleports one out for the other. Skills are basically the same between twins with minor differences.
If current Gremory was forced to add them: You play as Sofie, Yufie only appears in some skills and in the ultimate animation and victory screen. (Also Yufie doesn't have any costumes because she's not playable, so she won't match with Sofie)
Reality: NEVER EVER

Chu