Hi Vicky,
So much for BIL understanding. Does he realize just how much you do for his parents? As long as he knows they are taken care of, even if it is you doing it, he is satisfied with the situation.
That's not fair to you. You have your own life that you need to live. I'm not saying that if there was no other choices, that you should stop taking care of them, but there are other choices and your husband and BIL need to understand this.
Good luck to you and the family.
Take care,
Linda