Hi Rajesh,
Being the ancestral property, the property will devolve upon the legal heirs automatically.
After the death of Grand Father, your aunt (Father's sister) and your father have became joint owner of the property.
After the death of your father and aunt the ownership of the property will devolve on the legal heirs of respected person. Being only son, you have became the owner of the portion of the property.
As regard to the right of aunt, she during her life time had right to reside in the said property and equal part/ portion if the property if the male legal heirs sell/ partition the property. The husband of your aunt and his son being the legal heirs of the predeceased aunt have became the joint owner of the half portion of the said property. Although they can not sell or claim partition in the said dwelling house. Only if you choose to sell or partition the property their right will be to the said property.
Hope you have got the answer to your queries.