they naturally only stay in pairs but yes you can as long as the roo doesn't pick just one hen, if he does he and his chosen mate could really hurt the "outsider".
I have four hens and two males in one large 5 x 5 box with natural like cover. The more older/dominant male breeds all the females except one and that one seeks out the younger male. I would prefer just the one male there but I need to get another large area to move the male and the one female that prefers him to a seperate large box. Then again I do have three "pairs" that have thier own accomodations