New Delhi, Apr 30, 2008 : Vidya Balan will be the leading lady of the Cheeni Kum director’s next film. Pa , the next one to be made by ad filmmaker R Balakrishnan, has Amitabh Bachchan and Abhishek Bachchan playing father and son. Balki has finalized Vidya Balan to play Abhishek’s love interest. The filmmaker had earlier thought of casting Aishwarya Rai for the role, but later dropped the idea because it would have looked like a family union.