Harnessing senior citizen parents for money and property.

A daughter looking for help for parents! My parents are senior citizen, please note father of 62 age suffering from high blood pressure and diabetes and mother of 58 age suffering from low blood pressure. MY parents own 2 property one in which we live on the name of mother and other raw Land on the name of father. my father is retired from the post of principal from government school in Delhi and now a pensioner and mother is housewife. My father has four children 3 son and one daughter. My brother got married 3 years back. My father has demanded no money from them, most of the people knew this at time of marriage. Post engagement my brother lost the job as he was working as software engineer (Done MCA) and immediately same has been inform to girl's father from my father. My father didn't hide anything from them, with girl's father consent, marriage was done. Girl father has gave 2.3 lakh in cash on sagai as token of money in marriage. The entire expenses of marriage was endure by my father around Rs 12 lakh, provided no contribution from my brother side. my father gave jewellary to her on marriage. Similar as Indian wedding happens. Soon after the marriage, family discord started taking place and my sister in law always demand money gave by her father on marriage. Eventually, situation got worsen to handle as it was deteriorating health of parents and other sibling also got affected from it. My Brother always remains on her side. soon after they left the house and started living on flat which is own by girl's father. In-laws of my brother are threatening kind of people once they have threat to file case against us. After one years, on my marriage they put so many condition like 1. money 2.3 lakh, 2. To build separate house for them on land which own by my father. My parents didn't gave any consent for the same since he has other children to settle down in front of my bhabhi parents. Thereafter they come back to attend my wedding. they had no contribution neither money side nor effort wise from there side as being only the daughter and sister. Neither concern about other siblings future. Now, again same discord has stated taking place in home for money and property thing. And situation has such worsen that my own brother threat my own parent by way of finishing his own life they they dont do such thing. he is totally in control of bhabhi and her parents. This threatening situation was happening once in two- three months. My other sibling control him to not to cut his vein. my bother always says i will vanish you and me also if don't do as i say. This threatening situation happened so many time and reached to such serious level that my parents are sacred of there own son and Daughter in law and fear of damage of respect in society. For information my brother is not working since he lost the job but somehow fulfilling each and every demand of her. my bhabhi more into in her family. Now, i being a daughter want to protect my parent if something false can happen in near future. It will be a cautious approach to save life and respect in society. In other words where and how we can give our application and also do not reveal to them and other as i said it will be a cautious approach. please help!!