Property share

My husband is a uae resident and has 2 sisters in india who are married. He has spent all his earnings of 15/16 years for them and he is the one who married off the 2nd sister and took care of his family till date (there is no proof for all these). His mother felt pity for him as he does not have any money left with him now (being an NRI his account has zero balance) and he has two children so he was given 3 cents of land out of the 4 cents she had. After getting two loans, we finally managed to bulit the house and we are struggling to repay the loan. Now the husband of second sister had come asking for the share in the property including the house that we took loan to construct. His elder sister is a widow but she got share from her husband's property and now she too is demanding the share in the property. The mother in law said that she would distribute the remaining 1 cent among the 2 daughters but they want the share in the 4 cents including the house. Please advice as what needs to be done. Me and my husband are working from morning till night to repay the loans and meet the needs of the family. They came up with this issue only after we finished the construction of the house. Please advice as what needs to be done next.