Son and daughter in law harrasement

My Brother and sister in law are harassing my parents. My parents are aged 60 and 59 respectively and my brother is 35 and still not earning single peeny he always asks money. It all started after his marriage his wife always tells him that my parents property is his after them so no need to work ask them to give us money they are old now why do they require money. After marriage from day one she started creating differences between them and used to tell lies that my mom is give bad words to her and wants to beat her and then he use to beat my mom and give bad words to dad and after three months they left the house and took 3 flats from my dads (due to there mental harrasement my dad is suffering from Parkinson's ) after 7 years they pressurised my parents to take them back in there house and again started beating my mom and dad telling them to make house in there name for which they both are harrassing them even the house workers have seen him beat my mom and using bad words for dad. Her dad is equally responsible for this he gives them such advise to beat mom and dad they belong to such caste which gives her rigth to some Actrocity act, so she always tells my parents that i will send you to jail and even my brother tells her that harrass them mentally so they will leave the house and all property to us. They even harrase me due to which my husband stopped me from going there in 3 years of marriage i have hardly visited them it was after my first delivery i went to stay with them but they started fighting with me also and within 1 month my husband bought me back home when i asked them to stop them doing this things they gave me open challenge that they both will harass them to such extent that they become mentally ill they said " amhi tar denar tyana mansik tras tula kai karaychey te kar." Please tell me what can be done.