Originally Answered: Why cant I live with my sister when we are in foster care? I hate this?
You need to speak with your caseworker about this, and ask for a written notification of the findings that led to the separation from your sister. If either of you is in a therapeutic foster home, it may be that one of you has a need to work on your own issues. If one of you is significantly older than the other, they may feel one of you has been a parental figure to the other and needs to "learn to be a kid." If you are both old enough, and can contact each other, I believe you should campaign to be placed together as soon as possible. The longer you are placed apart, the more likely it is that they will make a permanency plan that has you placed separately -- assuming your parents are not going to regain parental rights and you are likely to be free for adoption. If you are or might be already legally free for adoption, go to AdoptUSKids.org and see what your profile says. If the worker has you placed separately and states that your plan is to be permanently placed apart, you have your work cut out for you, because they have somehow already determined you cannot be together -- ever.
All hope is not lost, however.
If you don't fight, you know they will win. Demand a guardian ad litem to represent your mutual interests with your sister's in the case to terminate your parents' rights, or if they've already been terminated (or it's a different situation like a death) to petition the court to not be separated. If you get no response from your caseworker, or you feel CAS is playing you, go to the mattresses. Get a petition going, contact the citizens' complaint website at your state governors' office, mutually start a Facebook page with your sister (to show us in the public that you both wish to remain together) to gain publicity and support, and call legal aid in your community to see if you can get a pro bono lawyer for your case.
It may be a matter of convenience for them -- that you will each be more adoptable on your own instead of together. But you and I know you two are better together --right? (In helping you with all this, I pray that it's true and that there has not been abuse or worse between you two).
They may perceive, if you are a brother, and particularly an older one, that you would prey on her. Sick as that sounds to you I'm sure. They may perceive, regardless of your gender, that the two of you together are manipulative or something. If you have behaved in a manipulative way in the past, it's no more than was modeled at home, or was done out of fear of abandonment by your family and/or this very nightmare -- being separated and/or sent away. Duh.
Good luck to you.