Hi, I'm new to this forum but I've kept bettas for a while now.
A male can sometimes be kept with females but he'd have to be a gentle, non-aggressive male--so know your fish! I have one beautiful male who isn't interested in any other fish at all, just cruises around making friends with everyone, never flares, never gets excited at seeing a female or a male betta. However, most male bettas are just too aggressive to keep with other bettas of either sex. If you do decide to try it, first make sure there are lots and lots of safe havens for the fish (sometimes the females will get very aggressive with an uncooperative male and tear at him, especially if he's outnumbered)--lots of plants, lots of things to hide behind/under/above, etc. 29 gallons is large enough so each fish an establish a territory so it should be interesting--but keep a close watch for a few weeks so if one fish starts tearing into any other fish, you can jump in there because you don't want murder in the tank. It may work out if all the fish are congenial but it might not. Something else you should consider is that a male in with a female(s) may breed and either the other fish may eat all the eggs or fry, or you may end up with hundreds of bettas. Are you prepared to deal with tending baby bettas?