At six months he is not mature. Adolescent human boys can mate and crow but that doesn’t mean he is ready to settle down and raise a family. Just ask the father or grandfather of any teenaged girl.
Some cockerels and roosters are human aggressive. There is always the debate about how much is inherited and how much is learned behavior, I feel it is a bit of both. Unlike you I do eat my chickens. If one shows undue human aggressiveness they are not allowed to breed. I haven’t had that problem in years so I do think the tendency can be inherited. But I also think some of it is learned.
That said, what you are seeing isn’t all that unusual in a cockerel. He’s trying to find his limits, especially if he is the only cockerel you have or happens to be the dominant one. I do occasionally see that behavior when there is no adult rooster in the flock.
You’ve let it go on longer than I would. The first time I see any hint of aggression in a cockerel I walk toward him. I don’t run or move quickly, just slowly walk toward him. They are basically cowards and really like to sneak attack. Usually they will walk away. I keep walking toward him until he does walk away. When I stop and turn around to go about my business, if he starts trying to sneak up behind me I walk him down again. I keep doing that until he just walks away when I turn around. That is usually all it takes.
I’ll allow a cockerel to attack me once. When that happens I catch him, carry him around awhile, force him flat on the ground and rub his back with vigor, and peck at his head with my fingers. Let him know very clearly that attacking you is not an option. When I finally let him go I may walk him down as described above if he doesn’t just walk away. This usually works but if he attacks a second time he has run out of chances.
Sometimes this teaches him to respect all humans, but often it teaches him to respect you. It’s very possible you can teach him to respect you but he will still attack any other human that comes in range. I don’t accept this behavior either. Your sister may need to go through this process with him herself but any other people could still be in danger. Kids are especially vulnerable, partly because they don’t know how to behave calmly around a rooster and partly because their eyes are so close to his level.
I don’t go out of my way to provoke a rooster or cockerel. If I need to examine the chickens I’ll lock them all in the coop and get the rooster first. After I’ve examined him, I toss him outside before I grab a hen in front of him. To me this is a reasonable precaution. But if I need to handle a hen in front of him, I will. When I do this it’s normal for him to get between his flock and me, that’s fine with me. But it is not normal or acceptable for him to attack.
It may be too late for any of this to work for you. Since you are not getting rid of him and do not cook your chickens, you may just have to put up with him attacking and injuring people or keeping him confined where he cannot get to people. It’s your choice.
