Can a property owner restrict the forceful entry in the property?

I am asking question on behalf of my Mother. She is a widow & of 65yrs. We have 2 properties. A shop which is in name of my mother & my late father jointly. & a house in name of my late father. My father died in Dec 2011 & there is no will of father. My brother married in July 2013. Since then his wife has been threatening me & my mother that she will file a false dowry case against us if her demands are not met. She wants that we should give shop to my brother so that they can sell it & also half of the flat to them. They wants that we should divide the flat by erecting a brick wall in DDA flat. Since my fathers death both my brother & elder sister has not taken care of my mother. They frequently quarrel with us & use abusive language. What should we do in this case as we dont want to sell our flat? Kindly guide me if my mother can restrain them from entering out home as my brother & his wife are not living with us since Nov. 2015.?