The veteran stars in the film, albeit in a brief role. He first appears in a photograph, when Waheeda Rehman walks into the ancestral home and refers to Bachchan Sr. as her husband.
Yep, Bachchan Sr. enacts the role of Abhishek's grandfather in the film.
Bachchan Sr. eventually appears on the screen towards the end, during a crucial part of the climax.
The sequence brings the real-life father son together. Of course, we wouldn't like to spill the beans, but the sequence is vital for the film.