Answer
(Fatwa: 1504/954/L=1433)
If at the death time of your grandfather and grandmother (Nana and Nani) none amongst their parents was alive then all the property of your Nana and Nani shall be divided into 8 shares, after due rights proceeding inheritance. Out of which each son shall get 2-2 shares and each daughter will get 1-1 share. The detail of the division is as follows:
Details:
Sons: 3×2 =6
Daughters: 2×1 =2
Total: 8 shares
It is not right for your Mamu to compel your mother for signature by giving some money. Yes, if your mother withdraws her right from the shop by taking some money happily then it is allowed.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband