How to prove whether a will is fake or not?

I have registered documents containing my mother's authentic signature and thumb impression. This includes land registry deed and two registered Wills. My cousins have produced two wills in Civil Court claiming them to be genuine in which my deceased mother has allegedly willed our house to them. The earlier of these wills is a registered will but the latest will is unregistered. The registered will also contains thumb impression claimed to be my mothers but I know for sure that the signature on both these wills and also the thumb impression do not belong to my mother. The registered will produced by my cousins does not contain any mention of earlier registered Wills drawn by my mother and I know it is a fake will even though registered. How can I prove this forgery and crime in court and send my cousins to jail? If the thumb Impressions do not match, will that be enough to prove the crime? I am Hindu.