I don't think I am going to contribute to my brother's rehab fund.
Rehab centers are expensive. How come you don't want to contribute to your brother's fund?
I spent a lot of money on him already
You should support your brother if he is trying to better himself. Family is expected to support family.
I am honestly not going to support his rehab.
Honestly, I don't blame you because your parents should be funding the entire thing because you aren't really responsible for him. You don't deserve to have this burden dumped on you. You can always support him via different means, like emotionally.