You sound like my friend's sister and BIL,
My friend who has never married and lived in the house with her mother snce she was born, the sister is married and has a perfectly nice house just up the road from them.
My friend has redecorated, put a new kitchen in, paved her garden to make a parking space (lives near a university so parking on street is now almost impossible) put a ramp from the parking space to the house to accomodate her mother's wheelchair (paralysed after a stroke) got a special lift put in from living room to her mother's bedroom, and adapted the bathroom. She got very little financial assistance for any of this work, and no contribution at all from her sister and BIL, or their grown up DC.
Friend's mother died a few years ago, and left the house to my friend, and some money to the sister and grandchildren.
Friend's sister forced her to re-mortgage the house, so she could get a share of the money. I was incandescent with rage, because she really bullied and forced her into it. And they still demand money from my friend, five years on.
They guilt trip her into paying their debts and all sorts of things.
Sorry, bit of a rant there, I just get so mad at their greed and selfishness.