I think my brother is f***ing gross
Why do you think your brother is gross?
He gets nastier every time I see him
It's okay if our siblings disgust us. Depending on the sibling,  you can't help be disgusted if they live in terrible ways.
I would do anything to not being related to him.
Well I don't think you have to go that far, you should just agree to disagree with him about the way he lives. You don't have to like everything about him.