How to sell own share of properties without willingness of other

Respected sir. my grand mother has 3 floor building .. after she passes away ,she left behind an undivided property . she has 3 sons . All the three sons live in each floor . My grandmother managed to deed with his 3 sons with equal properties. but she didn't divide the floor and mention any one's name that who will live in which floor..but after she died all the three sons decide to live in each floor. problem is that my my father is my grandmother's 2nd child living in ground floor, my father is financially weak wants to sell his share of property "the ground floor" but my both uncles are not showing interest and we know they will ask us to not to let the floor sell. being jealous they wants that my father should n't sell his share of property ..plz tell sir "to sell the share of my father's property, is the (uncles) opinions and their signatures are needed?? they threat us that you will not sell your property untill we agree ?? is i correct ?? we live in ground floor. my grandmother dived her property and all one's name but didn't mention who will live in which floor.. plz sir do reply.. for this act of kindness i am ever grateful to you.