I think this has been asked and answered before. Yes their are two keyboard players, the take turns in playing rhythm and synthé(keyboard effects) in BCBG, the main rhythm keyboard player is Cedric Guezula whilst Geremie Kitubu plays mainly Synthé,if you've noticed, it looks like Geremie is technically more skilled than Cedric as i have seen him setting up or correcting Cedric at concerts.
Concerning Wenge Maison Mere, it's the same principle were the keyboard players are concerned, one plays rhythm(like piano) whilst the other plays the synthé to manipulate sound for special effects. On guitars, BCBG has no position for mi-solo, in Maison Mére,they have a position for mi-solo so they have four guitarists at a time ie from left to right is the bass guitarist who stands next to the rhythm guitarist and on the right hand side you have the mi-soloist who acts as a second rhythm guitarist but producing higher notes and often in sync with solo/lead guitarist who is at the very far right on the stage.