My grandparents have 3 children (My father(death 2017), his brother and elder sister) The biggest mi

My grandparents have 3 children (My father(death 2017), his brother and elder sister) The biggest mistake my father and his brother made was buying properties in the name of their parents. After the Hindu Succession Act (Aug 11th 2020) we began to fear about possible outcomes. My grandparents always wanted my father n his brother to share their properties with their daughter (Damn selfish). My father even let her (his sister n family) stay in one of our places (free of cost for more than a decade). Their selfishness doesn't end their and we fear that they might take advantage of this Hindu Succession Act 2020 to get something for their beloved daughter. We were thinking about a Will / Gift deed but that would definitely give them an advantage to ask for favours. Can she (my father's sister) really claim part or anything from our property (in our grandparents name)? What else can be done to protect from them?