Property share

My husband is the only son and have two elder married sisters well to do. My husband was the second holder in this flat. My husband is not educated. My husband and My self were staying with his aged parents, as my husband salary was not sufficient to run the house and look after his sick parents. I also had to work. After my father in laws death, my husband's elder married sister told my husband that she will stay alone ( without her son and daughter in law ) with their mummy in our house and look after her. Due to this my husband and myself shifted to rented house. slowly within a year his elder sister's son and daughter in law starting in our house and his elder sister and her son told us that they want to buy this house and will pay us our ( husband's ) share. Both mother and son told my husband in my absence, to give the original agreement of the flat so that that they can get loan on the flat and give my husband his share and my husband without checking with anybody gave the original Flat agreement to them. Now five years are over and till date their have not paid us a penny. when my husband ask they just say we do not have money now to pay you. we will pay once we have. They have their own business. please help us as we are not in the condition to file case or take any legal actions. as his son has political contacts.