Can daughter claim in father's property after his death

Mother and sister conspiring to grab all father's property--- My father died on 25 june 2016, i am staying in the same place so i take their care, after his death my younger sister started influencing my mother and has done her nomination on all Fix deposits of my father, she is also a joint bank locker operator of my parent's locker, Now my father had purchased a flat 25yrs back by his self earned money, but he had registered it in my mother's name, i doubt that my mother will make a gift deed of the flat on her name. what shall i do to get my valid share on all Fix deposits, flat and Gold.