Don't know what to do ?

Your mother needs to find a solution to keep all of you together. She's allowing an 11 year old child to make a life-changing decision? That is ridiculous. She needs to be the parent and take charge of the situation. Undoubtedly she is having a lot of trouble dealing with this as well. Yes, you will have to step up to the plate and help out a lot. Tell your mom you want everyone to be together and you will work with her to get to that outcome. Try to remain calm and as reasonable as possible. You are all in a tough situation. Good luck.