We have 2 roosters and 15 hens.  The roosters and the youngest hens are almost a year old now.  They seem to be doing great. We had had two other roosters, one was killed by a mystery predator a little before they all started coming into their 'randiness'.  We re-homed the other when it seemed we clearly had too many roosters for our hen count.  So there are two roosters left and they were chicks together and get along though they also compete a lot.  They seem to tag team the guarding of the group, and if one goes to mate a hen the other often rushes over and knocks him off to mate her instead. Initially they were harassing the hens terribly, and there were two of the more passive girls that I had to separate from the group temporarily for their own protection (one had been injured and one had had a serious molt and just seemed to feel puny), but the roosters have grown up some and seem to be gentler on the hens, and the two hens got reintegrated without difficulty after they had had some recovery time.  We have our oldest hen who we often call a he because she used to have the roll of flock guardian before the roosters came and grew up.  She is still pretty tough with the roosters and I hear her try to crow a lot more these days.  So though the roosters are clearly above her now, she hasn't fully given up her role as protector and doesn't take too much attitude from them.  We've only had chickens a few years but that is our experience.  They all free range on about an acre and get locked up at night.  My eight year old is outside with them often and keeps track of the chickens' social scene.