my father had purchased a site from a lady (it was her self acquired property). he has a registered sale deed for the same. The lady had huge piece land out of which she divided and sold them to individual buyers. he has been paying property taxes, the EC states my father as the owner, bbmp tax reciepts also reflects my fathers name. However recently it came to our notice that the lady whom he purchased the property from has gifted the entire land to her grandson. we were shocked to see the same transaction as because she had already sold us a piece of that land long back. The mutation records shows transfer of property from lady to grandson. Is this transaction valid ? do we have a legal case to go ahead with? note: the property we purchased does not have khata.