Husband and wife are joint owners of 5 immovable properties and they want that in case of death of one other one should become sole owner and on that others' death it should devolve in some specified manner/share to their children. So whether both husband and wife should write separe wills or there is no need at present to write the will and after the death of one the other should write it?? what would happen in case both die simultaneously or in gap of 1-2 days???