Securing property rights of Second wife from Children of the first deceased wife

3 years ago

My father in law has a flat in mumbai suburb which is the property that we are discussing about. He is 78 yrs retired govt servant living with my mother in law who is the second wife and mother of 3 daughters. All three daughters are married.
My father in law has one son aged 51 from his first marriage. He is based in Daman for last 22 years and a businessman. He is married and has two kids. Recently he approached my father in law for all financial help stating that he has applied for divorce and also he has no money left in his account. My father in law inspite of his meager pension savings, travelled to Daman and helped him financially and also settled him to stay in a rented apartment. however after 2 months he has started threatening my father in law that he wants more financial aid or needs a share in the property. My father in law is very clear that after him the flat should go to his wife till she is alive and is not in favour to sell the flat. The son is threatening of dire consequences if he does not sell and give him the money. What should my father in law do to safeguard the property for his wife.
My father in law has already given his son all the forwards from the sale of an ancestral property in 2011.