Joint property dispute

Hi, We have an ancestor property in Delhi. I live on the ground and the third floor with my family and my brother lives on the 1st and 2nd floor of the building. At the time when floors were decided (verbal agreement and not mentioned in the papers), there was no 3rd floor and my brother just took the 1st and the 2nd floor. Later after a few years I built a 3rd floor with a room on the 4th floor with my own money. Now, my brother has become greedy and wants a 50% share from the 4th floor which we have agreed because we want to resolve it peacefully. However, my brother now is threatening us that he wants to swap the ground floor with his first or second floor.I have been living on the ground floor for more than 40 years. I have rented my 3rd floor to a tenant and recently got a notice from my brother asking a 50%share in the rent. Please tell if he has the right to ask for the share in the rent from the floor which is in my possession and also what legal actions can he take in this scenario. I am emotionally attached to our house and don't want to sell it. Can my brother force us to sell the whole property? Usually how long does it take for cases like these to get resolved or settled ? Can I still give my floors on rent and not share the rent with him? My brother in past has rented his floor for more than 10 years and we never bothered him. Please tell what best options I have in this scenario and what else my brother can do.