Hi, property is the self acquired property of the your grandfather, during his life time he executed a will in favour of your grandmother so she become the absolute owner of the property.
2, Your grandmother during her life time has executed a will to 1 son and 2 daughters, they become the absolute owner of the property after the demise of the grandmother so others have no rights over the property.
3. Will come into affect only after death of the testator.
4. If you want share in the property you can challenge the will before the court.