My only sibling has borderline personality disorder and is very dangerous. She stole my identity once, before the Internet, tried to make me legally responsible for her student loans and was cyber-stalking me recently, so if I am paranoid, I have come by it honestly. I keep myself low key so that she doesn’t find me or what I am doing. It was so bad that I couldn’t even tell my parents my youngest children’s actual birth dates because she tried to get a SS card using my oldest son’s birth date when he was first born. Luckily, the mail came to my house. My husband has her and her known acquaintances blocked on his FB and those of our children. Many of my H’s FB friends are from his childhood and I don’t know them and they don’t know me and I am fine with that. His friends whom I do know are aware that I am not comfortable with FB and they will PM him if there is any reason to communicate with me. My friends text or call me and know that I don’t do FB.
Maybe I am a bit extreme but I would rather be off the grid than worrying about sis.
TM