Howdy John. First of all, thanks for being brave enough to share the kinds of thoughts you have shared here. You took a risk because you want to get help and that takes courage. Kudos.

I’m also glad to hear that you and your brothers have moved on. Here’s hoping that all of your family has learned whatever it is you all needed to learn from this situation and that you all grow strong and even more loving as a unit.

I got to tell you man, I was not going to respond to this because it is way out of my depth. The most I know about dealing with unwanted thoughts, the kind that can be crippling, are the depressive type. The depressive thoughts I suffered from used to “tempt” me to commit suicide on a regular basis. As a matter of fact, I wrestled with depression for years. When it got to the point where I knew my life was in danger, I went through a prolonged period of actively questioning those thoughts using self help techniques like inquiry as well as actively disentangling my sense of identity from them. It took roughly 4 months but by the time I was done I was never plagued with depressive thoughts again. But sexually obsessive thoughts… that sounds a horse another color to me.

Have you considered seeking professional help? You might want to think about that option. A self help tool you might also consider is called The Work, by Byron Katie. The questions are simple, straight forward and I have found the process to be very useful. Also, fighting your urges might make them stronger, in a sense. You ever heard the saying that what you resist persists? I’m thinking that dynamic might be involved here. Now don’t read what I am saying as an endorsement of incest. I am neither condemning or approving. Judgment isn’t my business. What I mean by resisting is, if you condemn yourself every time you become sexually aroused or every time you have a thought that you deem inappropriate about your sister, that attitude, that attempt at repression might very well increase rather than decrease the unwanted thoughts and emotions. So you can try forgiving yourself for what you did to your sister first of all. Now that you know better, you are doing better, according to you. Then secondly, when the unwanted thoughts and emotions appear next, rather than move into automatic rejection and judgment mode, simply notice them. Notice the thoughts as they appear. Pay attention to the way your body responds to those thoughts, in the form of arousal. Just sit with them. Then watch as they move out of your consciousness of their own accord. If your mind moves into hyper judgment/fear mode, notice that as well. Take a step back and become the witness.

But that’s all I got. Like I said, the above might not be helpful for someone with these kinds of thoughts/arousal habits. I do hope you find what works for you though.

Hello, it's good that you've come forward. Not many people would have the courage to do so.
I can relate to you in that i've experienced wrong sexual thoughts. Now I don't know if you are christian but since you said you're dealing with demons so you're either speaking metaphorically or you at least believe in evil spirits. Whatever the answer, I would suggest visiting a local church :)
If you're Religious or not the people there are a loving family, you don't have to share all the details but tell them you are struggling with sexual temptation, and that you need support from caring, understanding people, churches are full of them! Everyone lusts from time to time, it's something everyone can relate to.
Try talking more in depth with the local priest, vicar or pastor; they won't judge you they deal with these things a lot so just whack it a try. Explain to them how you feel, ask them to get rid of the thoughts or demons inside you and they'll probably pray for you and offer some advice.
Be open and have faith!
Outside of a supporting community try seeking counseling from a professional; the councilor shows you what to do, the community is the muscle that drives it!
I hope I've helped.