Answer
(Fatwa: 1328/1044/D=1431)
You and your sister did not become the owner of the amount only by nomination but it shall be counted your father’s property, which after his death became inheritance that shall be divided among his legal heirs according to Shariah. If your deceased father’s parents and wife have already expired and only you, your brother and sister are the legal heirs, then after due rights preceding inheritance, i.e. the expenses of obsequies, paying off debt etc, whatever remains shall be divided into five shares from which 2-2 shares shall go to both the brothers and 1 share to your sister.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband