Want to file a case against on my father's brother

My father’s(48) were three siblings including my father and my grandfather died when my father(elder) was 18 years old, my father got married first then my next elder cousin got married but younger(42) one didn’t get married till he reached early 40’s and they had some liabilities so they shared whole liabilities in three parts and started their own paths(as separate families), as my younger cousin haven’t get married my grandmother lived with him, all my parents and cousins do rice cultivation (almost daily laborers), by accidentally my elder cousin died, as compensation LIC gave 30K to my grandmother, she got 1.5L from govt. to build house, and she is also dialy wage earner, my younger cousin has been taking all these benefits from my grandmother. he got married 4 years ago from now, my grandmother and cousin together earned money for 20 years after my cousins took their own paths. now the day came, my grandmother got sick and has to stay on bed for forever. we decided to take care of her health month by month(my grandmother has to stay with us for one month and next month with my cousin), till here we don't have any problem. but now my cousin demanding for money which is spent on her for entire 20 years and not even talking about benefits he got. so I would like file a case against him, could you please advice me on