Cancellation of settlement deed

My grand father aged about 78 years, has 4 children (3 daughter and 1 Son) My grandfather is an state govt retired pensioner he purchased land of 2400 sqft in 1983 and built two house in that land. one for self and one for renting it. In 2012 my grand father wrote a will in which he mentioned the property should be equally divided to all the four children. Later in 2014 he's son cancelled the will and registered settlement deed to his son(grandson) in April 2014. My grandmother got to know this informed to all daughters later with the help of daughters my grandfather cancelled the settlement deed which was registered within 20days. Few months later my grandparents were with their elder daughter's house for 3 months there they received a notice stating that cancellation of settlement is not valid and in that notice my grandfather's address was different and my uncle son had sent the notice from my grandparents address claiming for possession he don't have any Id or address proof in my grandparents address. Still my parents live in that house. Electric city bill is in my grandfather name regularly tax is paid under my grand father. My uncle's son filed case against my grandfather claiming house belongs to him. As the rent was regularly collected by him.