Dax Shepard slams claim that he cheated on Kristen Bell with Julie Andrews' step-granddaughter

Dax Shepard is shutting down rumors that he was unfaithful to his wife, Kristen Bell.

The "Ranch" star took to Instagram on Thursday to address a report from DailyMailTV that claims he cheated on Bell years ago with Kayti Edwards, the step-granddaughter of Julie Andrews.

Edwards alleges in the article that, after meeting Shepard through mutual friends in 2005, the two developed a "brief," casual relationship. She claims they rekindled their romance at a private party in Hollywood in late 2009, while Shepard was about two years into his relationship with Bell.

"I was house-sitting for a girlfriend of mine in Hollywood and there was this party ... I saw him and we hadn't seen each other in a few years. So it was like a very friendly, 'Oh my gosh, I haven't seen you in forever. Nice to see you,'" Edwards alleges, claiming Shepard "threw" her in the photo booth with him. "We went back and made love, we had sex twice and he stayed until the next morning. I didn't know he had a girlfriend at the time, he didn't seem to care."

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Photos embedded in the article show Shepard and Edwards passionately making out, but it's unclear when they were taken. Daily Mail claims they are nine years old, but according to Shepard, the timing is inaccurate.

"Hey Daily Mail, that photo is 13 years old, not 9," he wrote on Instagram. "Also, Kayti has sold stories to tabloids about Matthew Perry, Jack Osbourne, Kid Rock, and now me. I look forward to her next one. Fingers crossed it's about my #1, Brad Pitt :)"

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Meanwhile, Bell seemed unfazed by the rumors, taking to Instagram to share some exciting news of her own. "This is what your face looks like when you find out that @sarabareilles has written a song especially for u on a super secret project...," she captioned a selfie.

Bell, 38, and Shepard, 43, started dating in 2007 and eventually tied the knot at the Beverly Hills County Clerk's Office in October 2013. Ever since, the lovebirds haven't been able to stop gushing over each other in interviews with ET.

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"She's a better person than me by a factor of at least six," Shepard, who shares two children -- son Lincoln, 5, and daughter Delta, 3 -- with Bell, told us earlier this month. "But still, even if I do one-sixth of what she's doing, that's still a lot more than I ever thought I was going to do."