Probate of will

As I want to know that the property where I am living since birth, it is owned by my grandfather and he have transfered it to my grandmother name. After his death its owner is my grandmother and they have one son and two daughter.My father is the elder son from his other two sisters.I am the only son with one sister of my father and my grandmother leaves with us only.Later she had make a will for her property on my name due for love where my father had been one of the witness sign in 2010.In 2013 my father died and 2014 my grandmother died. Now after that I went for the probate to transfer the name.There I bave got no objection sign from my sister and mother. But when I went for the signatures for my two aunts , now they dont want to sign as they are demanding that this cant be the valid will as this property firstly belong to my grandfather then to my grandmother and they also demanding that there son and daughters also have equal rights there. So can I know that what i will do and is this will favour to mine .