How to sell a property where one of the joint holders is deceased

I want to buy a resale flat ( situated in Mumbai ) jointly owned by Father & Son ( both are Hindus ). As the father passed away a couple of years back , I want to seek the following clarifications before proceeding further in the matter. 1. Whether the surviving owner can sell the property by executing sale agreement all by himself ( signed only by him. ) ? 2. As the deceased co owner is also having other legal heirs ( Spouse & other children ) is it necessary that they should also join the surviving co owner in executing the sale agreement ? If yes, in what capacity ? 3. What other additional documents / precautions to be taken to safeguard my interest. Please enlighten me in this regard at the earliest as I want to complete the formalities as early as possible.