Your kidding me right? My bettas have been together for a year or two, they've never fought, and think about this, in the wild, bettas always live together, if they have enough space, they'll be fine
*deep breath* No, I'm not kidding.
Have you ever seen what a wild betta looks like? Here I will show you a picture.
They are very different than the long finned, brightly colored, domesticated fish we have today. Also, Bettas in the wild have enough space (shallow but long rice paddy fields) to retreat, and retreat they do. Our Bettas were originally bred to fight. They have become highly aggressive through selective breeding for fighters and typically do not back down until serious damage happens or death. They are NOT social fish. They do not "hang out" in the wild. They have territories that they are constantly guarding for intruders and only come together to mate.
You are incredibly lucky that your fish haven't killed, or seriously injured each other. Your situation is NOT normal and it is NEVER recommended to keep males and females, or males and males, together.
Advising people that they can is just asking for trouble. It is not worth the risk.
wow, that is so pretty, I love the wild betta, no wonder they got domesticated.
I heard you can keep 3 or more fish together, but you cannot keep 2. Only one male per tank, and a sorority of females, but it has to be more than two females or they will fight. The tank has to be significant though, 30 or more gallons with lots of plants and toys for them to each claim their own territory. Then it also depends on the personality of the fish, some do better in groups than others and some just don't get along ... But I am by no means ready for that kind of challenge, I am just barely managing to keep my one happy.
Unless you have been breeding your fish into living together the way OldFishLady has, then I would never advocate trying it. As LionCalie says, it is an enormous risk and is definitely not worth it. The situations in which it will work out are extremely rare. Not a good idea.
One reason it won't work so well with a female+male combination is that females don't have specific territories. They roam in and out of male territories, so they will come into contact with the males. If they aren't in breeding mode, chances are, they will simply tear each other to shreds. This is why sororities work - the females aren't guarding their own territories, they simply want personal space. Males, on the other hand, are guarding specific territories and won't accept interlopers.