Most inheritances where the owner dies intestate, create a tenancy in common. While you can sell your share, there are few people who would want to purchase your share. An action will have to be filed forcing the sale of the home if the parties cannot come to an agreement. If by chance it is a joint tenancy, a partition action would have to be filed to force the sale of the home.
It is a complicated situation and best solved by negotiation - consult a transactional real estate lawyer.
We are sorry about your delema,,,,,
Your best course of action is to make your feelings known to your family. At the very least, rent should be paid on your share of the property. It's not unreasonable to approach your sister's daughter and make her aware of your need to charge rent....
An unpopular move for your family but possibly essential for you, is consulting a real estate attorney to develop options.