Hello, so my best friend has a little beother(8 years old) and he is mentally unstable. He has something similar to autism (I think it's worse). He doesn't go to school, because he gets bullied even by teachers, but no one in his family believes him. He even goes to a psychatrist and gets bullied for that. He always throws things at his family when he's mad. Soon he has to take a test, which determs if he goes to a clinic for 4 months( he also has seperation issues). The doctors then decide if he will still live with his family or not. If that happens they'll also take my best friend with them, because they say that if one child is mentally unstable then the other one has to be it too. I think the reason is really stupid because she's the most stable in her family. What should I do? I know that I should worry so much because nothing is decided at the moment but it's driving her mad. I really want to tell my parents but my father would tell my mother and my mother would be like 'I expected it' or 'Her whole family is insane'. If I'd tell my little sister she would be happy because she hates my best friend. What do you guys think? (Sorry if I have any grammatical mistakes)

If they do move, try to keep in contact, perhaps you could meet up now and then. For now, maybe just be there for your best friend? I bet they don't want to move away from you either. My younger sister has Asperger's, which is not as serious but she hits people a lot, so I can vaguely understand the situation with your friend. Be there for each other, and just know that even if they do move, that you can always meet up.
I hope this helped in any way.

Thank you for your help, but her brother did the test and he passed! He even transferred to a better school, where he doesn't get bullied (his classmates are 3 years older than him). But still thank you! :D

Yay! I'm glad to hear everything went well!
:)