Flat Ownership

If ‘A’ and 'B' are co-owners of a Apartment in Mumbai , that is solely purchased by 'A', what documents should be prepared by ‘A’ so that the Legal heirs of B cannot claim a tittle to the property and in future the legal heirs of A get ownership of the property. What needs to be done incase demise of A so that the legal heirs of A get’s added to the property What needs to be done incase demise of B so that the A gets ownership to the Property without having to contact the legal heirs of B. All have good relations now and do not want to disturb it.