your sister-in-law is not adjusting in the joint family. judicial separation is what your brother wants or is it your family’s collective decison. will your brother be happy without companion and his daughter? is his daughter found of both the parents? what is the greviances both have?. what are the expections from each other.
what did she steal?your sister in law does not want any relation with you and your parents but is she stopping your brother and daughter from coming to your parents house?
there is normal wear and tear in every marriage. most of the time interfearance from parents and relatives (both side) aggreviates the situation. if there is so much of tension, why not the core issues are discussed and resolved. why not you arrange for the meeting between both the family resolve the greviances. or let them take help of marriage councellors then take the final stand. try to avoid 498a situation.