It sounds like there is possibly an issue with him. The brothers might attack him to establish dominance…set the pecking order. But typically the females don’t do that. Have you had a vet check the cockerel out? Make sure there isn’t some disease that causes the other chickens to try drive him away.

Other than that, you could try segregating him for a while, give him some extra food to eat to help make him bigger. Once he gains some size and age, (and providing he is healthy) they will likely stop attacking him.

And if you ever have a rooster that attacks you or the other members of your family that might enter their pen, let me know. I have a cure for that too!

That could be but I forgot to add in the details is that he is the only one that stands out. He is a Silver Pencil Rock and two others are 2 Barred Rock, 2 partridge Rock and all the rest are Rhode Island Reds.

When I was raising chickens, the breed didn’t seem to matter. I had all sorts mixed together and they got along fine. The roosters will definitely vie for dominance so don’t be surprised that one starts killing off others. We managed to keep 3 I think at any given time. The “big boss” tussled with them a bit but once they established their pecking order, it settled down. If you ever lose your “big boss” the other roosters will start fighting again to show who the new boss is. But hens usually are pretty benign. That’s why I wondered about an illness.