Hi. Have a mean cat and need help
 

Well the cat that is mean is Frilly. We got him and two of his brothers at the same time. He is being mean to Treppie (brother) and Kizzy (first cat we got) and was wondering what i could do about him being mean to both of them? Any help will do thank you

Firstly are they both sterlized?
Your cat may be frustrated. Entice him to play with toys. Get the toys on a string and play with him. Also those lazers are great to get them going.
Cats also like to perch. Make sure that he has a place where he can be at eye level so he can clearly observe his surroundings.

I'm a fan of stuffed toys for cats so they can rake, chew and dig with their back feet on it. You can put your own hand in a safe place on the toy and engage Frilly with it. Soon he will probably attack it on his own. The toy should be about the same size he is.

That said, my own cats use a small piece of rolled up carpet the same way. I can get them started by poking a slender stick under it.

That's a little sketchy for details. What do you mean the cat is being mean to it's housemates? Is it attacking? Is it just swatting? Is it biting? What starts it? What steps do you take to stop it? Have they been to the vets or separated lately for any length of time? A complete history of what/how/when/why would be helpful in order to give you the assistance you are requesting.
Thank you.