We normally recommend one rooster for every ten hens or so. In a large flock, there is often more than one rooster, with no problems. In smaller flocks, it's a greater risk. However, many breeders keep significantly greater numbers of roosters with their girls--one rooster for every two, or one for every five. We don't recommend it for the typical backyard chicken situation because there is always the risk that your girls will get overbred. However, if you do end up with more roosters than you bargained for, the good news is that it is still quite possible for your roosters to coexsist peacefully, especially since they were raised together from chicks.
A rooster is the natural head of the pecking order in the flock and when there is more than one rooster in a pen, they usually have a pecking order between themselves. In other words, one of the roosters is the "top roo" and the other is on the bottom. They will occasionally face off with each other with raised hackles, but the bottom rooster usually does not normally try to assert dominance with the top rooster, so it never comes to an all-out fight. The top rooster will have all the mating rights and allows his hens to eat any treats first, then he will eat some and lastly the bottom rooster may have some. If the bottom rooster tries to secretly mate a hen, the top rooster will chase him away from the hen.
The more space they have in this situation, the better, because close quarters can add to the tension.
It may sound like a sorry life for the bottom roo, but really it is not. If you consider a pecking order like waiting in line, everyone is always in the same order in line for food, water and treats; someone is always in front, someone is always in back. If someone tries to cut in line, there will be a scuffle until the line is back in order. As long as there is plenty of food and water for everyone, then even the ones who are in the back of the line get plenty to eat. This is true of any chicken flock, even if there is only one or even no roosters!
Young roosters can often be overzealous in their matings, so you'll want to watch to make sure the hens are not being injured from overmating. If you start to notice severe feather loss over their backs, wings or back of their heads, they may be getting too much attention from the roosters. We do sell chicken saddles, which help protect their backs, or the girls might need a break from the guys.
If the girls need a break, we would recommend removing all the boys and keeping them together. Many roosters can co-exsist peacefully in one pen as long as there are no hens to fight over. Don't separate the boys from each other or they might forget that they know each other and start fighting when they are re-introduced. That would guarantee you would need to re-home one of them. But as long as they keep their pecking order intact, they should co-exsist peacefully. If the bottom roo ever decides to seriously challenge the top roo, they may not be able to live together anymore and you may need to rehome one of them. Read more about keeping multiple roosters together in our blog. You can find suggestions for rehoming chickens in the related questions below.