Its not that simple FPSC has a very complex system of allocation if someone vacates a seat. To keep it bit simple, first of all you have to check whether person vacating seat belongs to open merit or your province. Then you have chance, other wise not. Moreover, if a girl in open merit vacates a seat, she will be succeeded by a girl (thanks to a brainless judgment killing spirit of "open merit"). Above all, there is lengthy procedure of litigation, so its not that easy.