I can not imagine the pain that you are going through in terms of your sister, but I can imagine the pain of the dp and the incredible terror and suffering it is causing you. You sound a lot like me. When my brother was going through terrible depression and suicidal thoughts, I decided that I would fade into the background and not cause problems. I didnt' want to cause my parents any further pain, and I didnt' want to cause my brother further distress, even though I wanted to connect to him. I know it's not the same as schizophrenia, but the ache of having someone you love "gone" in an emotional/mental way is intense. I can't understand it all, but I understand some of it. Just keep moving forward, living day to day, and hopfully things will get better. Take care.