How do i deal with parents who are putting to much pressure on my sibling?

Talk with them and discuss an agreement to come to.

I have gone this before, but this is what i did, they wanted her to do this and that  and i was sick of it. so one day when she was told to clean the bathroom i said no, i was sticking up for her cause it was rude. then i told mom and step dad why and they finally understood. maybe talking to them will help and explain why will help you and your sibling

Dbecause there are negatives surrounding ding it