How do they know?

Yesterday, I was hoovered by an ex-boyfriend. We had a very acrimonious breakup over two years ago. He was a total slime ball - turned out to be married (told me he lived with two "bible thumpers" who didn't approve of dating, and they let him crash on the couch in the living room, so he could never take me to his place!) - and I discovered he was with several OW at the same time. His poor wife. He managed this, because he worked for an airline and could travel and cover his tracks. Anyway, I read him the riot act when I found out all this stuff and it was a brutal ending. Of course, I was devastated, even had terrible, horrible nightmares afterward. And now he comes out of the blue, just when I am at a very low point and still emotionally distrught and trying to recover from this last narc and hoovers me. Claims I have been on his mind a lot and says nothing of what he did in the past. WTH? Does he really think I would just jump back into his cesspool? And my narc sister did the same thing - recently contacted me after 12 years of no contact and started claiming I was the only one in the family she loved and that she wanted to help me. Uh-huh. Right. This is the same person who treated me like garbage when we were growing up, constantly gave me the silent treatment, and 12 years ago volunteered to help me move and when she got angry with me for not wanting to carry out a hair brained scheme she had, left all my stuff in the road and drove away leaving me abandoned in the country with no communication or transportation to get out. Why do I need her back in my life? It's like they have a sixth sense that you are weak and prone to attack and come out of the woodwork - I am utterly amazed at their extra perception. Of course, I hit delete on the email from the ex-supposed boyfriend. It is a bit harder to ignore my sister, but working on that and have been rather successful. I have decided to ignore her emails and voice messages now and not to pick up my phone without looking at the caller ID. I am praying to God constantly that he will help me find peace and some normal human beings!!!