Hello- Thank you for asking the question. I have over 30 years of experience working with individuals, couples and families & am happy to reply.
I am very sorry to hear about this.
Having worked with persons with Autistic Spectrum Disorders for 30 years- I have a deep understanding of how difficult parenting can be and when something such as this presents, it can be extremely devastating.
It is not uncommon for children with Autistic Spectrum disorders to be overwhelmed with the physical and sexual aspect associated with puberty and acting out with a sibling in this way is not surprising given the often poor decision making process that often is operating in psychological make up.
Your son is acting out of primitive drives and although he may understand that this is wrong---- and obsessive compulsive scenario such as happened can unfold.
I have seen many adolescents with Autistic Spectrum disorders-going through puberty and responding favorably to medications such as Prozac which has been show to inhibit the sexual impulse and acting out behavior and this is the direction I would suggest that you take this.
If I were you - I would be open and honest with your children'
children's Pediatrician and explore the possibility of managing the sexual acting out with medication. Your Pediatrician may want to involve a Child Psychiatrist to consult regarding medication management and this is fine.
You children have disabilities and they are not sexual perpetrators. This is how you have to look at this and reach out to those in the community that can help work your family in a comprehensive way to address this problem with the goal of extinguishing the behavior.
See the following links for more information on this:
Behavioral Modification approaches are often very successful in treating these obsessive compulsive sexual issues.
IF you need assistance finding experts in your area to help you with this- feel free to respond with your Zip Code and I will be happy to help with this.
In the meantime- try and re-frame this problem so that you can see it as a manifestation of your children's disability vs a perverted sexual process.
Kindest regards, Bill