Property Matter

We are 4 brothers, 2 sisters and my mother is above 88 year. I am eldest in all of them and handicap and retired from private job. I have got 3 daughters who all are married and son.1 of my brother and both sisters don't live in the our property and have complete interest in the property and try to create new conspiracy to harass us so that we leave that place. we have got 3 floors in total Ground first and second and on second floor.we have only 1 room constructed on second floor in which we live. I've to get my son married for which have to construct a room on second floor. I know my siblings would not allow me to do the same however I don't have any other option left as of now as my son is sole earner and got my daughters married from his savings. My all siblings are at least 10 to 12 year younger to me. I am the one who build this property with my mother.1 of my brother and sister does not have family and are above 50. How I can go for the construction on the second floor as one of my brother know law and might have got the power of attorney on his name at time of my father got expired and all of my siblings would definitely interrupt while constructing floor. I also have the documents of the property having my father name on them. My brother has already constructed a BARSATI on my roof. As of now I am staying on second floor and roof belongs to me. Govt. allows 4 or 5 floor while we have only 2 and half floor constructed. Kindly assist me how I can bold out all the obstacles to get my son married.