How Strong is our case???

I have asked this question earlier and i am thankful to all the responses received. I am asking it again as there were few things that wasn't clear and more information was needed. We are three sisters, all married & lives in different cities away from parents. We are in a dilemma whether to file a case against our only brother who has taken over all the property (approx Rs 5 crores of land) of our parents. Our parents died recently, and before dying my parents was taken to the registrar office by my brother and have given a statement that they are transferring all the property to my brother's sons and completed all the formalities of property transfer.A video of the same has also been made at the office. Later on my parents told us they did it under the pressure and threat from our brother. My father also gave us a HANDWRITTEN LETTER which says that our brother has threatened them and due to this pressure they gave the statement and transferred the property. The letter also states that our parents wanted the property to be shared between us and our brother. We are Hindu and our parents died on Nov 2016. Now my Question is: How strong is our case? What are the chances of winning? Looking forward for your reply. Thank you