Seeking legal protection for my parents?

Hello, My parents living with my sister in law as my brother has a touring job and also my sister in law has some severe medical issue such as she is suffering from acute epilepsy. We didn't know about her problem, her mother and elder brother cheated us without telling anything they performed a marriage in Feb 2015. We knew this thing in oct 2015, when she got fits. She conceived in 2016. Now the situation is because is living with my parents she always tries to live with her husband separately but the reality is she is not mentally stable, she is not able to take care of my brother’s 2-year-old boy, any time she can get fits and after that, she was senseless and unconscious and my brother has a touring job. Is, the problem is she and her brother (living in a same city) are always creating a problem for my elderly parents, they always give police dhamki to them for any single things. I'm requesting here please help me and suggest some legal requirements so that I can protect my beloved parents. Thank you