In Birth by sleep, which FF guys do you want to see in it this is my list.
Young Cloud(well the game is based ten years before KH)
Young Aerith
Young Leon/Squall
Young Yuffie
Zidane
Blank
Vincent
Dagger
and Zell.
Cloud/Aerith, Squall/Rinoa, Zidane/Garnet, Tidus/Yuna as well as everyone else.