benami property title suit

My grandfather purchased some property in the name of brother in law some 40 years back and is living and using the property as absolute owners for the last 40 years.A title suit has been filed by us for title of the property but defendants have now filed a petition to reject the title suit in court pleaing that such title suit is barred under benami transactions prohibition act.please advise any solution in the mattet and weather rejoinder should be given to the case also including adverse possession and law of limitation.are there any exceptions in benami prohibition act?what if the property was purchased before passing of benami prohibition act.