I wouldn't suggest it. Bettas can be very tough and harass the females untill they die if the females dont want to breed and the male does.tinybetta said:
You could get away with having 3-5 females in a tank with a male, but there would have to be a lot of hiding places where the females could get away from the males (These would include turned over pots with a hole, ornaments, large amout of plants, rocks to hide behind, etc).
How big are the tanks that the males are in?