Harrassment of my sister

Hi my family comes from a very simple and humble background. My father is a very simple and honest person. My sister got married in 2008. The family background of her in laws was not checked by my father. With the husband of my sister there is no issues ... But the problem lies with her father in law and mother in law 1. My sister and her husband managed to get a home of their with the help of us. Not a single penny has been spent by the inlaws 2. Even inlaws has not have their own house or property or money in bank .. 3. His father in law will always abuse my sister reasons My sister tells him for not taking bath for days My sister tells him to change his pant as he often does pee and sits in the sofa My sister tells him to puja path but he doesn't want Night he sleep in nude position And more.... Her mother in law though always pretend that she told him but never ever we found in front of us... So there is always fight in my sister house for these nonsense reason what to do. As we are tired with him even though his own son shouts at him often.... Plz reply