The Zindagi Na Milegi Dobara star reportedly has a cameo in the film, while the rest of the cast is yet to be finalised.
A source told The Times of India: "Excel will soon make an official announcement about the film that will go on floors sometime next year.
"Ranbir and Hrithik are very good friends who've never had the chance to work together before. Finally, it's happening."
Akhtar and Sidhwani previously collaborated for the film Karthik Calling Karthik.
It has been suggested that real-life cousins Kareena and Ranbir are to portray brother and sister in Zoya Akhtar's next film, which is rumoured to be an autobiographical tale of Zoya and brother Farhan's real relationship.