Property Division

Hello and Namasthe, My late Father-in-law ( died in 97 ) has a 60 x 40 site registered in his name in Bangalore . My Mother-in-law is still alive and my husband is the eldest and he has a younger brother and a sister who is married and 2 deceased sisters. My FIL has written a will stating that , half of the ground floor belongs to my husbands younger brother and the other half to one of the sisters ( as she was mentally handicapped and unmarried but deceased now ) and the first floor belongs to my husband and the rest of the floors to my husband's younger brother. Further the will states that as long as my MIL is alive, she can enjoy the benefits of the property but she cannot do anything else regarding the property like maybe changing ownership, selling etc. But the thing is , there is no first floor constructed. During my FIL's time, only part of the ground floor was constructed ( for Bakery business for my BIL ) and since then my BIL has built a structure ( for his Hotel Business ) on the rest of the ground floor ( on the part meant for my handicapped SIL) . So how do we divide the property now and implement my FIL's will. We are currently in the US and my BIL is very manipulative and didn't take care of my SiL she was in a govt. mental institution at no cost, but he benefited from use of her property. Now he wants to transfer the property in my MIL's name and develop it, but we don't want to transfer the property to my MIL's name. So please suggest the best way to divide the property legally. Sorry about the long question, but I had to specify the details. Thanks in advance for your valuable advice.