Karan launched Sidharth in his last directorial venture "Student of the Year" and has worked with Deepika in his home production, "Yeh Jawaani Hai Deewani".
The "My Name is Khan" director had recently said in a Twitter chat that the duo will make a good on screen pair.
When asked about this, Johar told reporters, "I agree. It is a good looking pair and they should definitely do a film. I think Sid and Deepika will look amazing together. And everyday there is a new rumour, Deepika with Sid and Deepika with Fawad (in a film)..So I think this has to happen very soon."
The dysfunctional-family drama, which stars Fawad Khan, Alia Bhatt, Sidharth, Rishi Kapoor, Rajat Kapoor and Ratna Pathak Shah, got rave reviews and has done a business of over Rs 45 crore within a week.
Rishi, who plays a 90-year-old grandfather in the film, said he constantly had fights with director Shakun Batra.
"I worked on the film for 22 days and there was not a single day when I didn't fight with him on the set. You can ask the entire star cast, we used to fight everyday. And not on some creative issue but only execution," Kapoor said.
Pakistani heartthrob Fawad, who plays a gay character called Rahul Kapoor in the film, said initially he was a bit nervous to take on the role as he was not sure how the audience would react to it.
"Towards the end I came to the resolution that it is just
another person in the family, there should be nothing shocking about it. The way that dealt with it is wonderful," he added.
The actor said it is a welcome change that people today are accepting homosexual characters on screen.