Simply because the rent receipts are in the name of your uncle he does not become an owner of the shop. You must be having the title deed of this shop by which the shop was purchased by your grand father. In whose name has the shop been registered? What is the nature of litigation pending in the subordinate court? If you can prove that the shop was purchased by your grand father then you or your father can claim the shop to the extent of their lawful share. Whether or not it can be claimed as ancestral property depends on more factors than one.

It will be unwise to predict the outcome of the case in the court.

you have stated that shop was bought in name of uncle . if it is bought in his name he would claim to be absolute owner of property . it is necessary to go through the case papers to further advice . litigation outcome cannot be predicted .

If the said property was bought in the name of your uncle by a registered deed or the said property was gifted to your uncle by a registered deed of gift during life time of your grandfather then your father can not claim.On the other hand if your grandfather died intestate and left the same in his own name then your father have equal right with your uncle.