As per latest Sc judgment daughter's right to ancestral property does not arise if the father died before the amendment to Hindu law came into force in 2005. The father would have to be alive on September 9, 2005, if the daughter were to become a co-sharer with her male siblings. The amendment to the Hindu Succession Act giving daughters equal rights to ancestral property is applicable even for girls born before the law was changed in 2005
Property inherited upto 4 generations of male lineage (i.e., father, grand father, etc.) is called as ancestral property. The right to a share in such a property accrues by birth itself, unlike other forms of inheritance, where inheritance opens only on the death of the owner. The rights in ancestral property are determined per stripes and not per capita. This means that the share of each generation is first determined and the successive generations in turn sub divide what has been inherited by their respective predecessor.
Your grandfathers property does not comes under the head ancestral property . So after the death of Grandma and Grand father the property divided equally among his legal heirs( His Childrens). Your father is passed away then his share is allotted to his legal heirs(you and your mother )