Brother threatening father

We are two sons and one daughter.My father is a retired person having two houses and agri land and drawing monthly pension.My mother died when we are around 20 to 26 years.My elder brother had never taken any responsibility and married on his own immediately after mothers death.Myself a govt employee and retired father togethet built a house in the site purchased by my father in service and got sister married.I have taken care of my father for13 years meanwhile my brother came back and joined family and residing in that house and we moved out of home and staying in rented house. My brother enjoying house,other house rent,agri land and fathers pension by threatening father.he is not dare enough to spelt a word as he beatens him. Problem is sister and sisters husband expired leaving 2 girl teenagers as orphans,but my brother didnt help them and let my father also help.I joined them in govt hostels and bringing in holidays.now im threatened that he will swallow those properties which are on my fathers name and leave my children also helpless.pls advice what precautions should i take!