Owner of mother's property after her death.

Hello, I am a PSU Service Holder, currently living in the city of Jamshedpur in the state of Jharkhand. I don't want to reveal our identity that's why I am not naming here anyone. We are 3 siblings. Eldest is my sister, who is married and lives in Jamshedpur with her husband and 3 children. Then, the second one is myself. I am also married with 3 children. And the third & youngest is my brother, who is also married with 2 children. He is a Govt. Researcher and lives in Mumbai. All we siblings have 3 years of age gap among us. My parents had acquired many land properties in their lifetime and also built 2 houses in Jamshedpur. The first is the one where we live, and the other house was meant for renting purpose. Both the houses are in my mother's name. My parents built these two houses so that after them one house should come to me & the other to my brother. My father had also purchased lands in 9 different places in his name. 6 were in Jamshedpur, 2 in Ranchi & 1 in Bokaro. All these places are in the state of Jharkhand. Until 2012, and as per father's old will, all the land mentioned above was to be divided among all 3 siblings equally. That is; 3 lands in the rural Jamshedpur to be transferred in the individual named of the all 3 siblings. And the remaining 3, which are located in prime & industrial location of the urban areas of Jamshedpur City were to be equally divided among all 3 of us, which means a land of 15 kattha to be equally divided as 5 kattha each among all 3 siblings. The two plots in Ranchi was supposed to be transferred in the name of both the sons and the Bokaro land was to be given to her daughter. At that time my mother had no will of succession, but it was known & completely understood to all 3 siblings that both houses were to be given to both the sons. This decision of our parents was in complete knowledge of our sister as well as was conveyed to her in front of her husband in year 2008 only. In the mid of 2012, I got transferred to Maharashtra for my service, & I moved there with my wife and 2 children. One of son who was studying in college in Jamshedpur stayed back to live with his Grandparents and take care them. Towards the end of 2014, my father's health deteriorated all of a sudden and he passed away in April, 2015. This came as a shock to my mother, and she survived her last in Feb., 2016 in Jamshedpur. In the shock of my father's death I applied for my transfer to my home town, which was granted & I moved back Jamshedpur in Nov., 2015. My mother passed away in Feb., 2016. In the month of July, 2016 when I had gone to collect the rent of our's other house, the tenant told me that they had already paid the rent to my elder sister. When I enquired the same with my sister, she told that the ownership of that house has been transferred to her name. When I asked how ? She produced a will of my mother stating that the other house is been given to my sister. And it says nothing about the house where we live in. When I enquired more deep into this, I came to know that all the lands in the name of my father has also been transferred to my sister's name through a new will of succession, claiming the old will to be null & void. The suspicion part started when this transfer was done without the notice & knowledge of both the brothers. Also the date of new will of succession of my father is just 4 weeks before his demise. And the date of my mother's will of succession is just one & half months after my father's death, when my mother was depressed. Also, this issue was never discussed either by my father or by my mother with me or my brother. We, both brothers suspect that our sister had misled my parents in their ailing period of illness & depression. I still had the old will made by my father. Also, the new will signed by both my father & mother was done when both their sons were away from Jamshedpur. Can law help me in this fraudulent case in getting us justice ? Please advise.