Disputes Amongst Siblings Regarding Property Ownership.

My grandfather in his will mentioned that the land property in our village will be transfered to my father's name after the death of my grandmother. Even after his death, when my grandmother was still alive no siblings of my father i.e. his 2 sisters and 1 brother raised any issue regarding this decision. But now that after her demise they all with the help of village talathi are raising problems saying that the property is to be distributed amongst all as they all are their children. Can they do this even after it is clearly mentioned in the will that the property is to be transfered to my father's name? Please do help.