Mark has kidney disease, more specifically polycystic kidney disease. If you are not familiar, cysts grow in the kidneys. Until the later stages they are small like a popcorn ceiling. However, Mark has some that are the size of small oranges. They cannot really be drained because they will fill up again. This is what has led to his kidney failure.
He has chosen not to make them your issue by keeping his medical information between he and his nephew, yet for some reason you have chosen to cling to everything he has going on.
Have you changed your mind about getting a divorce? I sure hope not.
It's time to move on.