The facts mentioned by you point towards a fraudulent transaction conducted by your brother-in-law. Depending on the detailed facts (which I am not aware of), this may perhaps amount to an offence of forgery, and may even amount to an offence under Section 467 of IPC (467. Forgery of valuable security, will, etc.), which may be punishable with a maximum imprisonment for life or up to 10 years.
Consult some local lawyer with full details of your documents and other facts. And, if so advised, you may also consider filing an appropriate civil suit for annulment of the transfer of the property, which appears to have been made by fraudulent concealment of material facts.
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