Return the property ownership to father

1.  Officially, IF you wish to mutate / transfer the name of your father in the property records, then stamp duty and registration is compulsory.  Since it will be a family affair the stamp duty and registration charges may be greatly reduced.

HOWEVER
2.  If the property originally belonged to the father (on records), who then transferred it to the sons and now if the sons want to re-transfer the property back to father, then with appropriate mutual consent terms the transfer agreement between the father to the sons may be revoked, after following due procedures.

In your case point no. 2 is not applicable since the father bought the property directly in the name of the sons.

Keep Smiling ... Hemant Agarwal