Prohibited work-relations, marital affairs, private liaisons, stolen glances, and secret exchanges can fill you with desire. Wanting what you can’t have is natural, so doing something that is forbidden or frowned upon can be quite exhilarating — especially when it comes to romance.

These actors and actresses played brother and sister onscreen, but when the cameras stopped rolling, they dropped the act and let their passions fly. Sure, it might’ve felt wrong or odd at first, but that didn’t stop these Hollywood stars from stepping out of their roles and into real-life relationships…

1. Michael C. Hall and Jennifer Carpenter: Dexter followed Hall in the eponymous role of a serial killer with a heart of gold. Carpenter played Debra, Dexter’s sister. The actors fell in love, married, and divorced during the filming of the show. 

2. Selena Gomez and David Henrie: Between all the ups and downs of Jelena (Selena and Justin Bieber), Disney’s Wizards of Waverly Place siblings Alex and Justin shared a press-covered, off-screen relationship. It was more or less a rebound that didn’t last too long, but the two remained friends anyway.

3. Chris Pratt and Emily VanCamp: You might know him from Parks and Recreation or Guardians of the Galaxy, but Pratt also starred in the drama series Everwood. Between takes, he ended up dating his on-screen sister, played by VanCamp. He wasn’t her only sibling crush…

4. Emily VanCamp and Dave Annable: On the appropriately titled Brothers & Sisters, VanCamp and Annable played half-siblings. Their off-screen romance became so obvious on-screen the writers added a paternity mix-up, meaning they weren’t related in the film after all.

5. Blake Lively and Penn Badgley: On the show, the characters Serena and Dan from Gossip Girl dated until they become step-siblings. Meanwhile, the actors who played them were on-again off-again for the whole run of the show.

6. Ian Somerhalder and Maggie Grace: These step-siblings were Lost in more way than one. While stranded on a deserted island after a plane crash, the character Boone had the hots for his step-sister Shannon. The two tried dating in real life, but that didn’t work out too well.

7. Shane West and Evan Rachel Wood: Before you get worried about 13-year-old Wood dating 22-year-old West, rest assured: their romance didn’t kick off until 7 years after filming the TV show Once And Again. It was a brief relationship, and Wood married musician Marilyn Manson shortly after.

8. Ashley Greene and Kellan Lutz: The Twilight vampire clan was already quite incestuous as 4 out of the 5 adopted siblings formed couples, but Emmett and Ashley were not an item in the film. While they each had their own partners in the series, they ran into each other’s arms after the workday was over.

9. Robert Pattinson and Nikki Reed: Before dating Kristen Stewart, Pattinson quietly dated his vampire sister, Nikki Reed, while filming the first Twilight movie. Edward and Rosalie’s relationship is complicated, but not as much as the off-screen courtship.

10. Matthew Broderick and Jennifer Grey: Ferris Bueller may take a day off, but Matthew Broderick kept seeing his on-screen sister after work. Did he expect that this movie would provide a blockbuster role and a girlfriend?  

11. David Tennant and Georgia Moffett: After Moffett’s real father played an earlier version of Doctor Who, Georgia starred in the show as David Tennant’s adopted daughter when he was The Doctor at the time. She must really like the time lord!

12. Carrie Fisher and Mark Hamill: In an infamous scene of the Star Wars franchise, protagonists Luke and Leia share a kiss before finding out they are siblings. Filming that scene must have had a serious impact because the actors had a short-lived affair.

13. Jamie Campbell Bower and Lily Collins: These two lookers played adopted siblings in The Mortal Instruments: City of Bones. Clary and Jace already had a lot of chemistry on-screen, and the actors portraying them dated on and off, but with sparks always flying.

14. Dean-Charles Chapman and Nell Tiger Free: In Game Of Thrones, Tommen and Myrcella Baratheon share little screen time, but they’re brother and sister… with parents who are brother and sister. Don’t take the show too much to heart, you guys.

15. Maureen McCormick and Barry Williams: Marsha and Greg make up 2/9ths of a wholesome family in the 1970s sitcom The Brady Bunch. What’s not so wholesome? Maureen and Barry kissing between takes of playing step-siblings. Even Maureen felt it was weird!

16. David and Tamela Mann: These two lovebirds had already been together for over 20 years when Tyler Perry offered them roles in Meet The Browns. The only catch: they would have to play father and daughter! They pulled it off perfectly and probably had a lot of fun shooting it.

17. Katherine Heigl and Jason Behr: Long before Katherine Heigl became America’s favorite out-of-this-leading lady, she played an extraterrestrial named Isabel Evans on Roswell. She and Behr got together and broke up before ending the show.

18. Hayden Panettiere and Milo Ventimiglia: When Panettiere played Claire Bennett on Heroes, it became apparent Ventimiglia’s character Peter was her uncle. When they began dating, Hayden was barely legal and Milo was twelve years her senior, so it got a LOT of press coverage, which their relationship could not withstand.

19. Lauren Graham and Peter Krause: These two got to know each other back in 1995 while working on a sitcom called Caroline in the City, and were cast together again in the 2010 show Parenthood where they play brother and sister. An old flame rekindled, and they’ve been inseparable ever since.

20. Amy Poehler and Will Arnett: The comedic geniuses behind Stranz and Fairchild Van Waldenberg had already been married for 4 years before filming Blades Of Glory, in which their characters, brother and sister, are suspiciously fond of each other.