We are planning to buy a new flat in Mumbai. We want the flat to be name of my father (as first holder), my mother (as second holder) and myself (as third holder). The amount would be invested by each of us in equal proportion. We want the arrangement in such a way that, in case of death of my father, his share should be given to my mother. In case of death of my mother, her share should be given to my father (if he is alive). In case of death of both my parents, their share of flat should be in my name. We want to have these arrangement at the time of buying a flat so that it cannot be changed later on (by way of nomination or will). Is it possible do so? and how?