Yes, you don't have roosters and hens, you have immature cockerels and pullets, though since she is laying she's somewhat acting as a hen. Puberty can be a rough time. He is hopped up on hormones and is trying to wrest dominance. Since he is so hopped up on hormones he doesn't have any real control. He probably is not recognizing that she is accepting him. The other boys are also in puberty but probably at different levels. It can be a mess later too.
Often when they get through puberty they settle down a lot. Often does not mean all of them or always. And with three boys it can get and stay really messy as they mature. There are a whole lot of unknowns that could happen.
So what can you do? You can remove that cockerel. I don't know what will happen as the other two mature between themselves or with the girls but that specific problem would go away.
I would not leave things as they are. That is sometimes an option but not when that pullet is getting hurt.
You could isolate that boy and give him a chance to grow up. Sometimes, maybe often, when they get out of puberty the hormones settle down and they can dominate the girls based on personality instead of having to resort to force. How long would you need to keep him isolated? Maybe a month, maybe 5 or 6 months.
You could try keeping all three or two of the boys in a bachelor pad with no girls. They often don't fight if there are no girls to fight over. Many people keep multiple boys with a bachelor pad.
I have no idea which would even work for you, let alone which would be best.
