Kristen Stewart and Robert Pattinson backstage at the 2012 Teen Choice Awards in Universal City, California on July 22nd 2012.

Say what now?

Kristen Stewart cheated on Robert Pattinson? With “Snow White and the Huntsman” director Rupert Sanders … who is 41 years old and married with children?

So wait, that not only makes her a cheater … but a home-wrecker too?

Damn, Bella!

According to US Weekly‘s latest cover story, the 22-year-old “Twilight” actress was caught by photographers hugged up and making out … and they have the photos to prove it.

Sanders — married to British Vogue model Liberty Ross, 33 — has two children, ages 7 and 5. During his marathon makeout session with Stewart, “it seemed like they couldn’t get enough,” according to one photographer.

People Magazine‘s latest issue covers the same story, along with this:

“Kristen is absolutely devastated,” says one source. “It was a mistake and a complete lapse in judgment.”

The hookup with Stewart’s Snow White and the Huntsman director Rupert Sanders occurred recently, the source says.

“She wasn’t having an affair with Rupert. It was just a fleeting moment that shouldn’t have happened,” says the source. “She never meant to hurt anyone. She’s a good person who just made a bad choice.”

And now, K-Stew has issued a public apology:

“I’m deeply sorry for the hurt and embarrassment I’ve caused to those close to me and everyone this has affected. This momentary indiscretion has jeopardized the most important thing in my life, the person I love and respect the most, Rob. I love him, I love him, I’m so sorry,” Stewart said in a statement Wednesday.

Up until today, Kristen Stewart has never spoken publicly of her relationship with her “Twilight” co-star Robert Pattinson, who has probably heard the news by now.

Poor guy.