It looks like the romance between K.Stew and R.Pattz may not be as everlasting as that of Bella and Edward.

Kristen Stewart ihas been caught on camera cheating on her beau Robert Pattinson with Snow White and the Huntsman director Rupert Sanders, PEOPLE reports. And if that's not enough, Rupert is married with children. Yikes.

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Robert Pattinson Kristen Stewart  

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"Kristen is absolutely devastated. It was a mistake and a complete lapse in judgement," a source revealed to PEOPLE, adding that it wasn't an ongoing affair, but a one time deal. "She wasn't having an affair with Rupert. It was just a fleeting moment that shouldn't have happened," the source added. "She never meant to hurt anyone. She's a good person who just made a bad choice."

This story could be chalked up as another salacious rumor the tabloids fabricated for magazine sales -- but Us Weekly has pictures to back up the story in its latest issue. Check out the cover.

Kristen Stewart cheats on Robert Pattinson - Us Weekly Cover

Eep. Even that one picture is pretty incriminating. But is that going to split Robert and Kristen up for good? After all, Rob and Kristen have been spotted out laughing and smiling together just last week at Comic-Con. But Us apparently also has pics of Kristen and Rupert involved in a "marathon makeout session" (...their words).

FYI: Rupert, 41, is married to 33-year-old Vogue model Liberty Ross and the couple have two children together, ages 7 and 5.

Okay, so let's have it... thoughts anyone?

Photos courtesy of Fame/Flynet and Us Weekly