Does my aunt have legal rights in my grandfather's property

It is certainly an Ancestral property in the hands of your father. No, A and B (who are your Aunts) cannot claim any right over the property in the hands of your father. However, if you have any sisters, they are the co-parceners and have equal right like sons in the family.

The property can never be made self-acquired property.  If your father makes a partition, then after such partition, the share of your father in his hands will become his private property.  Similarly, the share that goes to your sisters will be their private property.  But, the same will continue to be ancestral property in your hands with reference to your children.  (Once you make the partition, then the share that falls into your portion will become your private property). It will continue as ancestral property in the hands of your male children, while it will become private property in the hands of your female children.  The Cycle will go on. 

It is believed that you are all Hindu.

The succession opens on date of death.

Who was 1st owner o the property; Your Great Grandfather (Paternal as per language of the query) or his father or his mother of his relatives from his father’s side or his relatives from his mother’s side?

What is date/month/year of death of 1st owner and then your Great Grandfather?

Was his mother/wife alive as on date of his death and how many sons, daughters he had (pre-deceased and surviving as on date of his death)?

Was this property being jointly used/enjoyed in common?

What is the nature of this property say; rural, urban, agricultural land?

The said property is in which state?

The Aunts are married? What is date/month/year of their marriage?

What is date/month/year of death of your grandfather?

Confirm!