Source: Bang Showbiz NewsKristen Stewart has signed on to star in the sequel to 'Snow White and the Huntsman' but married director Rupert Sanders, whom she had an affair with earlier this year, will not be returning to the franchise as he is focusing on rebuilding his marriage to Liberty Ross.The 'Twilight Saga' actress has signed on to reprise her role as the fairy tale princess, but Rupert - who helmed the first movie - will not be taking part in the new project following his affair with Kristen.The filmmaker is completely focused on saving his marriage to Liberty Ross - who played Kristen's mother in the movie - and so studio bosses will find a new director.A source told RadarOnline.com: "The script has already been written and production will begin late next year.Â "However, Rupert Sanders definitely won't be a part of the project. Rupert didn't want to be a part of it to begin with because he is desperately still trying to save his marriage. The search is still on for a new director."It was previously reported that Liberty, 34, gave her husband an ultimatum after he cheated, telling him he could not be involved with the sequel if he wanted to be with her.A source previously said: "Liberty let it be known in no uncertain terms that Rupert can't direct the sequel to 'Snow White and the Huntsman'."Kristen was dumped by her long-term boyfriend Robert Pattinson - who plays her on-screen husband in the 'Twilight' movies - after the affair was revealed in July.Â However, the heartbroken actor has since taken her back following her "momentary indiscretion" and the pair are currently on a promotional tour for 'The Twilight Saga: Breaking Dawn - Part 2'.