Last year, my granddaughter, Allison was in the hospital with pnemonia. She is the absolute favorite of mine and my husband, (shush, don't tell anyone else, LOL!). Her mother had two other kids at home who were ill, so everyone was generally miserable. I also had a terrible cold. And even though I wanted to be of help to the whole family as well as visit my precious girl in the hospital, I couldn't for fear of making her and her sisters even sicker. It broke my heart, but there was nothing I could do.
Try to picture your jw mom and sister as being in the same situation. They are mentally ill with brainwashing, and there's nothing they can do. It makes it more difficult for you, but yur kids are definitely better off not being exposed to them.