Rightful Owner of the property

This is regarding my husband's parental apartment in Kolkata. My father-in-law before dying left the house to my husband and my mother in law whom too we lost recently. My husband's estranged sister and brother-in-law had complete control over all the household and all assets as we were not in Kolkata at the time of his mother's death. My husband unfortunately not only lost his mother but also the access to the household. It was my father in law's wish that my husband owns the property after my mother in law. nnI need to understand following details :n1. How to check the current ownership. Checked banglarbhumi.gov.in but unable to find the apartment details.2. In absence of any paper work how should we proceed. Not sure we could access the apartment without dealing with my husband's sister & brother in law would make it difficult for us. Can we get the copies of the deed etc. n3. Any other advise will be helpful.