Property transfer

A very good evening sir, if you kindly help me i will be highly obliged to you my question is....the flat i live with my husband ---is jointly in the name of my husband and father in law. my mother in law is dead already. my father in law is 84 years of age. my husband has one married sister who is the legal heir of the property after my father in law's husband has invested and still investing for this flat throughout. he is solely paying tax,maintenance,and also doing all his duties towards his father staring from insurance to what ever required. he is giving all comfort to him. but he is no way settling the issue in my husband's name.only he is verbally saying that this property's owner is my husband. my sister in law is coming here time to time and she is no way respectful to her father is keeping the option open and giving only vague words to my husband. for which my husband remains upset and relation in family becomes father in law has already done some nomination of amount for her but that does not mean she will not claim.. actually he is a peace loving person and so not want any sort of quarrel at home. my father in law is very tricky person he is not taking any step to declare or bring no objection from daughter that she would not hv any claim after his demice. pls tell me how can he get legal help and how can i help him mrs.indrani kolkata