Dark Betty,
I am so sorry for you, your sister and your entire family. A trauma like this does impact more than the person to whom it happened, and despite how exhausted you feel I think you are doing a very good job of identifying your own emotions in this while dealing with how the situation is bringing up memories for you. Please don't beat yourself up about how you handled your own assault, you should not feel guilty that you didn't report it or continued to see the man responsible. Sexual trauma impacts a person on so many levels, destroys confidence, self-image etc. it takes many years to make sense of it.
I am no expert in trauma or trauma recovery, so I can't offer any professional advice. But I can say that my sister was raped by a family 'friend' when she was 16 and much of what you've said reminds me of my own family's struggles to deal with it. I suffered enormous guilt that I wasn't able to stop her getting tangled up with a person I sensed was toxic. I've always felt I should have done more to keep her safe from him. My mother too just wanted to ignore the whole thing, and my father became withdrawn, muttering comments about getting a shotgun etc. He never did and things smoothed over, but to this day it is a topic not discussed in the family house. It's been buried and there is some estrangement between my sister and my parents as a result.
Just know you are not alone. I think the best thing you can do is keep the lines of communication open, be support for your sister as you have been and perhaps it's time for you to seek counselling to deal with your own trauma. You can also encourage your parents to talk it out, with a professional or in some other way. They could ring a helpline perhaps. It sounds like you are already doing so much and they must take some action to deal with their own response to this so you and your sister can be free deal with yours.
Good luck, I hope you all find a way to heal.
