The sad truth is, many families do not want to acknowledge sexual abuse within the family. My brother, a doctor, told me of a patient who was in his 70's, and had molested many female members of the family since he was a young man, yet his family refused to report the most recent incident to the police. Even knowing that this man continued to be a danger to others in his family.

I think you did the right thing to send the letter to his fiancee...how she chooses to handle the information is her own issue (she may ignore it like his family does), but you at least know you did what you could, and she has been warned.

As for your sister, you cannot make anyone get help. I would recommend that you talk to her, and focus on the fact that you love her and don't want to see her in pain or suffering. Bring up the problems you notice, and suggest that talking to a therapist might help with these problems. You can even offer to help her find one and get an appointment. I would focus on your trying to help her with the problems she is having now, and steer away from the abuse as much as possible. Since she doesn't want to face it, if you bring that up as the reason, then it might drive her away from therapy. Once she gets into therapy, and starts to deal with her present problems, then maybe she will feel like she can deal with her past.

You are a very caring sister to be so concerned. But the key thing to remember is, all you can do is suggest, you cannot make her do anything. If, after you have offered her your advice and support, she still does not want help, I would recommend leaving at alone, at least for awhile...based on what you have said, she absolutely needs you in her life, to be on her side.

Good luck.
*hugs*
mj