Robert Pattinson Dating Riley Keough, 'Inseparable' [PHOTOS]: Kristen Stewart 'Devastated' By 'Runaways' Co-Star's Relationship with Ex-Boyfriend

Sources close to actors Robert Pattinson and rumored new love interest Riley Keough (who happens to be the granddaughter of Elvis Presley!) have confirmed that the two are in fact dating. This news is clearly not music to Rob's ex-girlfriend's ears. Kristen Stewart is reportedly "devastated" over the news of this union, especially because Keough and Stewart worked on the film The Runaways together. Insiders say that Kristen has voiced her sadness to Rob through mutual friends.

"They're inseparable," an insider revealed to the Daily Mail. "Rob loves the fact that Riley is Elvis's granddaughter - that's true Rock'n'Roll royalty in his eyes."

After splitting from Stewart in back May, the 27-year-old Twilight heartthrob began spending time with 24-year-old Keough over the next few months for various Dior events, since the two serve as the face of Dior Homme and Dior Cherie, respectively.

"Recently Rob and Riley have been spending much more time together since meeting through their Dior modeling connection and Riley has stayed over at Rob's Los Feliz apartment," the source explained. Rob and Riley (nice ring to that, right?) were recently spotted on a weekend rendez-vous.

"They have a lot in common - they both love LA, London, rock music and table tennis," the insider added.

Despite all of the time they are spending together, the source claims that they are mainly enjoying "short-term lust right now rather than long-term love."

"Kristen is emotionally volatile at the best of times and flew off the handle when she found out about Rob's liaison with Riley. She told Rob via friends she feels violated," the source said. "Kristen feels that she acted as mentor to Riley on her first film The Runaways, introduced her to Rob and encouraged her to make a career of acting."

What do you think of Pattinson's new girlfriend, Riley Keough?