father sold flat and made fixed deposit with the funds,no will

Hello Sir / Madam, My father sold his self-owned 1bhk flat in gujarat for 18 lacs in 2010 following a dispute ( elder son HIT HIM) with his elder son and daughter-in-law. We are 3 siblings. Eldest son(42) married with kid,daughter (45) married with kids and then me the youngest(38) married. We all are catholics. Father has made a fixed deposit of different amounts totalling to 18lacs and has put my name as second holder and former or survivor. As of now he is enjoying privacy and comforts by staying in my 2 bhk flat which is self owned BY ME in gujarat. All his expenses are being taken care of by the interest earned on fixed deposits & his bank job pension money for the past 4 years. My query is as follows--- 1. CAN my brother and sister claim the fixed deposits from state bank of india by putting a restraining order on his demise. i am not in talking terms with my siblings them since they hit my father. 2. Since he has made a fool out of me many a times and getting back in touch with them, i told him to make a will. he is reluctant to make a will. what can i do ? 3. What necessary actions and precautions i can take as of now and after his demise as to rightfully get 18 lacs and not to get entagled in legal cases Thanks & Regards Mr. D Mumbai