I bought 2 Silkie black roosters. They had lived together in a cage and partly a back yard in a House, Raised from chicks. They are now about 8 months old one of them always mounts the other and the other let's him. Even offering his behind and plumping his back. Then after they finish they fight. I have about 8 female silkies and 1 dominating white Silkie named Zeus and a less dominating white Showgirl. The 2 black silkies are brothers and they are always together. They don't even attempt to interact with the hens. We recently hatched eggs, Zeus is the father of 12 out of 13 chicks (one is a showgirl). I bought them to mate with my chickens for Silkie babies and they are the only 2 black rosters I have. Are they just more into each other? Help?