Melanie
Hi Melanie,
I don't know you, but after reading your posts, I feel for you, your parents and your brother. I want to make a suggestion that you are obviously free to either take or leave. Please hear me out and get the full concept of what I am saying, before taking anything on board as an indication, or discarding it.
Maybe your parents are the one's who really need the help here. You obviously have strength and aren't or are no longer faced with a tragic dilemma, that apparently has no solution. You've stepped back, you know where you are at, and had the courage to face something that many wouldn't be able to (hence I feel somewhat free to be so frank). While you are hurting big time, the pain that your parents must be feeling is a horrid thought. It's not a matter of them choosing Scn over you or them choosing you over Scn. It's more than apparent that they love you, but the cult has such a "hold" and "mind control" over them (as it does with so many) that they don't have a "choice" (this will be killing them). You do have a choice, and you have made your choices. I'm glad you have and they are good ones IMO.
My advice to you is to look at things from their perspective (despite how stuffed that perspective might be, or is). That's a big ask, I know. However, while your parents are in no frame of mind to look at your perspective, I don't see that you have any choice if you want a resolve. Why is it you that has to step up? - cause they "can't" and you can. Doing so will increase your understanding and love for them, and with that love and understanding, you may have a chance at some resolve.
Don't underrate what your brother is going through. He'll be on real wobbly ground right now, and will need support.
Your scenario is a bastard of a thing (for all concerned). I wish you all the best with it, and that through whatever means, harmony between you all is restored sooner rather than later.