How to act against false charge of domestic violence

My uncle was married for 19 years and my aunt filed for a divorce three years back and also stated that she was a sufferer of domestic violence conducted by my grand mother, my mother(sister of my uncle) and father, my aunt(sister of my uncle) and uncle. My uncle was suffering from dementia for 11years and my grandmother is 77ears old widow. My uncle was used to be beaten by my aunt and his son (who is now 18years old) whenever my grandmother was not at home. Now my uncle died 2days back in a rail accident and his son and aunt didnot bother to do all rituals. After requesting and begging them, his son did the last rites and has taken a video as a proof. Now they are threatening my grandmother to leave the house. What should we do now? Point to be remembered: 1.My uncle was a teacher of a government school, that was given to him when his father expired. 2. A general diary was made three years back after my uncle was brutally beaten by his wife and his son.All proofs were sent to the women's commission, commissionerate of police and human rights department but we received no response from them.