My wifeDemanding share on herFather's and grand father's property

Dear sir. Myself Deepak Kumar Dey. I am from odisha.But now I m living in nagpur. coming to the point . I got married in mother in law is second wife of my father in law but after death of first wife.He have three son and a daughter from first wife and two daughters from second wife. All was well till the last marriage of his first wife's childrens but after that my father in law diddid changed behaviour to my wife and her elder sister. Even he didn't spent anything in my marriage. He refused to buy a saree for his daughter for marriage. we did all the expenditures for the marriage. That was not the matter.The real matter is after the marriage of both daughter my mother in law,now she is alone......They (first wife's son) are torturing her. But my father in law is not listening anything. We want he should do something for my mother in law safety. But he just telling us that " after my death she will get her share automatically.we have no idea what are the rights for second wife .So my wife wants to get her share to do something for her mother. my father in law have 300 decimal i.e..3 acre land. so can we get share from the above. plz suggest what we should do .