Very entitled and obviously taking advantage of your parents. But I guess your parents may also be happy to spend time with their grandkids. Have they ever complained to you? If not then I don’t think there’s much you can do because they are very willing.
I had the same issues as you and eventually i just have up in hoping that my parents will help me. I would suggest that you source for helper or perhaps explore the options of getting your in laws help instead.
You should talk to your parents not your sister. If your parents wanna spoil and give in to your sis, there is nothing you can do about it… And this won’t change even if she have a helper.
Can ask her to share cost with you for helper, since you want to get your parents to help with your baby too?
every1 is living under different circumstances & there's background to everything...