A Family is not always made by blood lines. It is formed with love, respect, honesty and respect. Do NOT be torn by blood relatives that express their so called love for you in any other way. Sometimes it is best to leave the past in the past and find a new place, a new family for yourself. Surround yourself with positive people that will be able to support you emotionally and mentally. Do for yourself what your grandparents did not and your mother could not. I will keep you in my prayers. I also pray for your sister.
Be strong and by all means be true to yourself.