I'm laughing at my brother's seizures being back
How cruel is that? Is your brother having any other problems?
Yes. He started to hallucinate when he was awake.
Laughing at your brother having seizures is cruel. You shouldn't make fun of loved ones who are having medical issues, you should try to help them.
Make it stop? It's because I'm bored.
Being bored is not a good reason to poke fun at your brother's medical problem. How do you think he feels being made fun of things he can't control? Why don't you try apologizing, and making it up to him so you can continue having a good relationship?