Domestic Violence On Parents

My mother's parents stay with their two sons, daughter in laws and grandkids. The elder son has now taken over the family business of my grandfather, but he does not pay a single amount to my grandfather, rather the daughter in law forceful takes money from my grandmother from time to time. Also the kids of the second son also many times takes money from my grandmother. Ultimately out of the mere pension that the old couple gets from Government, only a small amount is left with them, and it becomes difficult for them to even buy all the medicines for themselves. Though the daughter in laws offer food to the couple, but the quality of food remains poor while they provide their kids with great food. My grandparents are sensitive and weak at heart and so they are not able to stand up and fight verbally over the issues and hence are left out to cry in their room. The house is in the name of my grandfather's elder brother, who stays just next door. I would like to mention here that the son and daughter in law of my grandfather's elder son are great and they take extreme care of their father and also sometimes help out my grandparents too. Please do provide me a suggestion about the steps that can be taken so that my grandparents can spend the rest left out years of their life in peace.