Property dispute

Me and my two brothers have a property (land) in a village in West Bengal. We live there in an ancestral house. The house has 6 rooms and each of us is using (living) two rooms for approximately 13 years till our mother passed away (father had also passed away). My father had not written any will. The land is also undivided. 2 years ago I decided to build a new house with modern facilities in some of the remaining portion of the land. For that they gave me oral consent. I had also acquired permission from the Panchayat Office. During the construction process they have not objected and the building has been completed around 8 months ago. Recently I have some dispute with my brothers. Now they are threatening me that I have to give them the 2 rooms of our ancestral building I am using or they will build new rooms above the new building I have made, though there is enough remaining place in the property to build new house/rooms for them. How can I keep the 2 rooms I am using in our ancestral building under my possession and also stop them from building rooms above the new building I have made????