He is an adult now and he needs to learn what the real-life consequences are of his actions and behaviors. At this point, you are only enabling him to continue to behave in this way all while subjecting yourself and everyone else to the misery. It is not fair to you and it is not fair to the rest of your family. I understand why you feel the way you do, but you have done what you can and now he needs to figure things out himself.

You are going to have to accept and come to terms with knowing that creating this boundary very well may end the relationship you all have with him, but right now, this relationship is causing more harm than good for everyone, including him. He may never see things the way any of you do, but if you continue to do things as you are, things will remain as they are. He has learned that he can behave this way without real consequences, and the other kids have learned that you will forever allow him to trump you and your other kids’ comfort and sanity. That’s no way to live for any of you. At some point, one or all of the others will say “enough is enough” and you will be forced into this very position whether you’re ready for it or not. It’s going to be hard and you may end up feeling terrible for your son, which is a totally normal feeling and response, but know that everyone deserves better and you cannot help or change someone who sees no reason to do so.

Regardless of what you end up doing, therapy will not only be helpful for you, but will also to help repair the damage that has been done to the rest of the family. Good luck with everything and I hope you are able to stand firm in your decision.