Property partition

Hi, Let me start from the beginning, my father purchased a land in Delhi in 1982 which was purchased as Power of attorney in the name of my mother as 100% ownership. After his retirement in 2001, he constructed ground + 3 floors on the said property. Ground floor -father, 1 floor - me, 2 and 3 floor - other two elder brothers living peacefully. We mutually seperated the floors but not executed any documents for the same. Father is living with elder brother (no.1) and mother is with me. I had come to know from some relatives that my brothers were thinking that since my mother living with me so I may transfer entire ownership into my name. Hence, I requested mother to transfer of ownership equally to all three brothers as equal share. We approached local deed writer and he executed registered GPA and Will along with notarised gift deed and agreement of equal share between we three brothers in 2012 Everything was smooth but after couple of month second elder brother who is living on 3rd floor has put some material in a room of ground floor and locked it. In 2014, he moved out to another rented accommodation in Faridabad and locked 3rd floor also. In between, property condition also deteriorating so I and 1st elder brother called him to demolish the building and construct it properly and asked him to execute the registry floor wise in our individual name, so that if anyone wants to live there he may, else he can sell his share. We also ask him to vacate ground floor room which he illegally kept on lock since 2012. He refused us by saying that neither he will vacate any room, nor he will let us do any kind of construction. My mother and father along with some relatives also asked him to do the partition mutually but he did not heed to any advice. He and his wife threatened us that in case we try to break the lock he will file a theft complaint against my father, mother, elder brother and me. My father and mother advised us if he is not listening to anyone than we may revoke the GPA and they will execute a new will in the name of me and 1st elder brother. Personally, I and 1st elder brother didn't like the idea of removing him from the property share. Now, I request all you gentleman to guide me how we can deal with such situation, as our family is growing and they also need big space and without selling/constructing the property we cannot do anything.