If you feel in danger of slipping into "terrible depression," then it might be good for you to explore that with a therapist.

The problems in the lives of your relatives need not be your problems. There should even be a limit to how much time and mental energy you expend on them. None of these people are ever likely to straighten out. From time to time you're apt to hear more sad news about them. That doesn't need to precipitate crisis in your life.

How wonderful that your children have grown up successfully. Pat yourself on the back for a hard job well done. You don't need to "adjust" to your sisters' screwed up lives. That's their problem.

You must have successfully separated yourself from your dysfunctional family of origin long ago. Otherwise, your kids wouldn't be doing so well. Obviously, heavy drinking and abuse is not what goes on in your life. Finish the job of separating. You don't have to be unpleasant towards your relatives. Feel free to send them a Christmas card. But I wouldn't go spending much time around people like that in their world, nor would I want to spend much time entertaining them in mine. If you're not drinking excessively and having all kinds of drama going on in your life, they probably don't find you all that interesting. If, basically, they are not actually bothering you in some way, then be glad they leave you alone and all you have to do is leave them alone. Keep it just that straightforward and don't create confusion for yourself.