RottenRiley,
My only question to them is "who brought you into this world? Wiped your Butt, fed you and took care of YOU! Isn't it now time for you to try and give back a little something?"
I am really sorry that this is even an issue, and in all reality it shouldn't have anything to do with being a JW or not, it is decency towards your Mother! There are people all over the world and in all walks of life that disrespect their parents in more ways than one. I'm sorry that you have to witness that within your own family.
On a very side note, do not become discouraged if they do something and your Mom praises them for it. I do not know your family situation, but she may do it to acknowledging that they care and helping herself know that they care, kind of giving herself the love from them. Mom's are great at seeing the little things in us and making a big deal about them. Be happy with the time you get to have with your Mom right now, one day we will all lose our parents and will wish we had them back.
I mean nothing more than to encourage you.
Love