Karan is first time teaming up with "Chennai Express" director Rohit Shetty, who will be directing the brothers' saga.
"While Rohit and I are extremely excited with the excitement RAM LAKHAN has generated.... We would like to say... IT HAS NOT BEEN CAST!," Karan posted on Twitter.
Rohit is currently shooting Shah Rukh Khan-Kajol starrer "Dilwale" in Mumbai.
The original cast of the Subhash Ghai's 1989 movie included Jackie Shroff, Anil Kapoor, Dimple Kapadia and Madhuri Dixit.
Pakistani actor Fawad made his Bollywood debut with Sonam Kapoor starrer "Khoobsurat" last year.