Senior Citizens harassment, Eviction and Property matters

I am the granddaughter of J (83) and L (81) (I am the elder son's daughter). My grandfather, J owns a self-earned ownership property in South Mumbai and lives with his wife, younger son (K) and daughter in law (D). My uncle and aunt, that is K and D have been mentally torturing and harassing my grand parents over the last few years. It has become very horrible off late and they ill-treat them through their words and actions. My grand father wants to sell his property immediately so that he can split the amount in half and give my uncle one half to buy his own property. This way they don't have to live together. But my uncle and aunt have refused to allow the sale of the property, and said they will not go anywhere under any circumstance. They want the full property to themselves, and are very greedy for the money. They are waiting for my grandparents to pass away. The flat's nominee is my grand mother (L). How can my grandparents take legal action to evict them? They cannot live with them any more. What is the strategy we must adopt? What is the least time intensive plan so they can lead a safe life here onwards?