What if my sister says that the house was bought with my parents' money? What should I do?

Take out your information related to the house, such as real estate license, invoices and tax bills at that time. It would be better if the real estate license is directly in your name, which has nothing to do with your parents' future will or even inheritance. They didn't give a penny at first, so they didn't get a piece of the action. In other words, without shares, there is no share contract. No matter how much your sister argues, it won't work legally. Because the law emphasizes evidence. Your mother is the best notary.