Cheating by sister and Binlaw

I am an NRI kannada lingaiath married to bramhin girl against parents/family wish, i was out of touch with my entire family for nearly 14 years and 2009 reunited as my mother was very sick. During this period with a trust and promise by my own Brother inlaw to invest in india i did transfered about 48 lacks INR since 2010 to my own sisters name, My BIL arranged to buy a plot in our own village with part of my investment and part by my mother investment (she sold plots), then he gave an idea to build a industrial shed in that place which will yield in arounf 30k INR per month for that he is going to invest for the construction eventually recover the same on monthly bassis for a period of 3 or 4 years. I agreed for that and return back to Dubai. after few days my BIL called me and said my parents are insisting to register the plot in my own sisters name as i have made full payment for the plot. I agreed for that with no choice. Years gone and in 2012 i was blessed with a baby boy from thenour relationship went out of reach with some personal issues. There was no good normal communication and in 2013 i asked BIL to take a dicesion to transfer the plot and i will settle the difference what ever i have to pay him, but he is not ready to transfer till today due to his own emotional reasons. I have evidence of all the receipts of payments done through bank which details the purpose of transfer to my sisters bank account. I have my BIL hand written communications, whatsup messages, eamil confirming the payments done, land purchased for me, my father is against for this cause - as supprting documents which clearly highlights the intention of buying that plot under my name. Here the money transaction is done to my own sister and all my plot related communication is with my BIL. Also my mother is no more and my father is blackmailing me to sign the ansisters property papers if i have to get my invested plot in my name. with an good faith and respect i have no intentions to fight but they need to understand as this is preplanned cheating. I am sure if i go to our law court i will get justice, but i need a professional advise if i have to file a case against my own sister. Please advise