He tweeted: "T 410 -NEWS NEWS NEWS !! I AM GOING TO BECOME A GRANDFATHER .. AISHWARYA EXPECTING .. SO HAPPY AND THRILLED !!!"
The couple have been married for four years, but have persistently batted away rumours that they are planning to start a family.
The 37-year old actress described her husband as potentially a "good father" in 2009, because of his role playing the parent of his own dad Amitabh in their film Paa.
Amitabh last year criticised the media for its speculation that his daughter-in-law and son were unable to conceive despite reportedly stalling her career in preparation.
