Who Is Kristen Stewart's Hookup, Rupert Sanders?

Before Kristen Stewart, 22, admitted to cheating on her boyfriend of three years, her "Twilight" co-star Robert Pattinson, few had heard of Rupert Sanders, the man with whom she had an affair.

Now Sanders, the first-time director of "Snow White and the Huntsman," finds himself in the spotlight.

"I think it's going to be a while before he can shake this off," Us Weekly senior editor Bradley Jacobs told ABCNews.com. "I'm sure he's personally devastated."

Meanwhile, Stewart's relationship with Pattinson may be the first casualty of the affair. People magazine is reporting that the 26-year-old actor has left the Los Angeles home he shared with Stewart and is in seclusion.

A source told the magazine that Pattinson is "heartbroken and angry," adding, "I'm not sure they'll be able to recover from this."

A rep for Pattinson did not immediately respond to ABCNews.com's request for comment.

Sanders, 41, a married father of two, issued an apology to People soon after Stewart issued her surprisingly personal apology.

Read: Kristen Stewart Apologizes for Cheating on Robert Pattinson

"I am utterly distraught about the pain I have caused my family," Sanders said in a statement to People Wednesday. "My beautiful wife and heavenly children are all I have in this world. I love them with all my heart. I am praying that we can get through this together."

Sanders is married to model Liberty Ross, 33, who, in an ironic twist, played Stewart's mom, Queen Eleanor, in "Snow White."

Just before news of the cheating scandal broke, she posted a single word, "Wow," on her Twitter account before deactivating it. Before that, an instagram photo of a cartoon down-and-out Snow White, crying and drinking with the caption "Not so pretty or so pure afterall …..," was posted by the user "libertyross."

"Snow White" was the English director's big break into Hollywood. Up till then Sanders had been a successful director of commercials.

The $170 million dollar film took in more than $380 million worldwide, and Sanders was in discussions to direct the sequel.

"His career was just getting started," Us Weekly's Jacobs said. "Now this is a major setback."

Sanders is 19 years older than Stewart. He also met his wife when she was young, as a student at London's Queen's College. "He was friends with my elder brother, but I was out of bounds until I was 18," Ross told the UK's Daily Mail earlier this month. "Once we started going out, though, I knew he was the one for me. He is a very special soul."

They married when she was 24 and he was 31.

It's not clear when the affair began between Stewart and Sanders. In May, the same month the photo above was taken of Stewart and Sanders having dinner in Berlin, Germany, Sanders spoke about his Snow White to the Huffington Post: "She played such a good version Bella Swan, people think Kristen Stewart is Bella Swan. She's not, you know? If you meet Kristen, she's wildly kind of giggly and vivacious and rebellious and naughty - all things that Bella Swan isn't."

The latest issue of Us Weekly has pictures of Stewart and Sanders kissing in Los Angeles on July 17. According to the magazine, Stewart tried to play down her appearance with an L.A. Dodgers baseball cap - most likely belonging to Pattinson, who can often be seen in rotating collection of American baseball caps.

On Wednesday, the "Twilight star" issued a public apology to Pattinson.

"I'm deeply sorry for the hurt and embarrassment I've caused to those close to me and everyone this has affected," she said in a statement to People. "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."