This is what I think is happening, the ML he used to be with ning and she was also talking to the guy that got the ML sister pregnant. Supposedly she is "dead" about she isnt and she is trying to kill anyone who comes close to the ML. The accident of the ML mom, son and ex was caused by the Ning. Then she got the ex involved to kill off the FL and when the ex could not kill her, Ning killed her off for not following the deal. The ML sister throws her self down the stairs because she doesn't want to involve herself with the baby daddy anymore, after seeing him try to kill the FL under Ning orders this is my theories on what I got from the story. Sorry if it doesn't make sense!
Hmm. Its a bit clearer now.. Thank youuuu ^^
Someone please tell me what is happening in this storyyyy. Im so confused with the translation!