Celebs who dated their friends’ exes: Breaking up can be an incredibly awkward process. It’s even more painful and weird when you and your ex have lots of mutual friends. Social situations can get really uncomfortable, and your friends feel as though they have to “pick a side.” Then there are the times when one of your friends actually does pick a side—the side of your ex. As in, your friend starts dating your ex.

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In some social circles, this is OK, if both people in the previous relationship truly have no more romantic feelings for one another. Dating a friend’s ex may also be acceptable if the previous relationship didn’t last very long or wasn’t “serious.” However, there are some people who believe that a friend’s ex is off limits, regardless of the circumstances of the breakup. That’s probably a pretty safe rule, because dating a friend’s ex could make things even more awkward at the next social gathering. Not to mention, this could break up friendships.

Apparently, there are some people in Hollywood who didn’t quite get the memo about not dating their friends’ exes. It’s pretty clear that on some issues, Hollywood plays by a different set of rules. Here are 12 celebrities who have dated their friends’ exes.

12. Ashley Greene

Actresses Nikki Reed and Ashley Greene both starred in the Twilight movies together. They also have something else in common—handsome actor Ryan Phillippe. Apparently Phillippe has been making his rounds in the love department after his divorce from Reese Witherspoon (the former couple also have two children together), and has a thing for actresses. Ryan and Nikki were seen at Winston’s in Hollywood, and drove off together in his car. Years later, Phillippe was seen with Ashley Greene, leaving Vignette Lounge with her. They were both trying to hide their faces from the camera. Maybe they were tired of having their pictures taken. Or maybe Greene knew she’d broken the “girl code” by dating Phillippe and didn’t want Reed to find out.