What to do family asking for signature so that I can't claim my right

Sir/mam, I am the first daughter to my parents and I have a brother. My family has 10acres of anchestoral property. And my father has 5acres of own accuired property and my mother has 1acres of land cum building in city that is earned by my mother. My parents are asking for a signature so that I can't claim my right to anchestoral property. They are telling me that anchestoral property is for their son and they will give me a share in their earned property in future. I guess it's a trick. Sir I want to know if I have any right in my parents property while they are alive. Can they be able to give all their property to my brother without my consent. I don't know whether to trust them. Because they are asking a signature by the terms that I willfully have no objection in giving my share of assets to my father I have no right claiming back here after. This is the kind of signature they are asking me for. So sir I really really need your assistance please help me to take the right decision