Your aunties (sisters of father) are not right to claim the entire property of your grandfather. Your father also deserves half of the property (i.e. double of the share of one aunty) if there are only these three legal heirs of your grandfather. If there was no other heir except these three (your father and two aunties), then the property of grandfather will be distributed in 4 shares, out of which 1-1 share will go to each aunty and the remaining two shares will go to your father. You can demand your aunties the share of your father and you can adopt lawful means to get the same.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband