1. Sophia Bush and Chad Michael Murray
CMM and Sophia not only dated, but they were married! The 'One Tree Hill' co-stars were only hitched for a few months before their divorce finalized in 2006, when 'OTH' was still on air.
2. Blake Lively and Penn Badgley
Serena and Dan have been on-and-off for basically the entire series of 'Gossip Girl,' but Penn and Blake broke up for good in 2010. The show just ended in 2012 so that's two years of awkwardness that they had to endure. Yikes.
3. Jessica Szhor and Ed Westwick
The reason these two 'Gossip Girl' co-stars broke up is still unclear, but we do know that like Penn and Blake, they ended things in 2010 but the show didn't end until 2012. You do the math...
4. Kaley Cuoco and Johnny Galecki
Kaley and Johnny dated secretly for two years before the secrecy finally caused their breakup in 2010. But at least 'The Big Bang Theory' is still going strong!
5. Joshua Jackson and Katie Holmes
Joey and Pacey were reportedly a real-life fling during the first season of 'Dawson's Creek.' The show went on for a few more seasons after that but Joshua and Katie clearly kept it professional.
6. Jennifer Carpenter and Michael C. Hall
The 'Dexter' co-stars play brother and sister on-screen, but in real life they eloped in 2008, separated in 2010 and got divorced officially in 2011. 'Dexter' is ending soon too, though, so luckily these two exes won't have to work together for much longer.
7. Nina Dobrev and Ian Somerhalder
This breakup just happened, like, yesterday, but Nina and Ian's duties as Elena and Damon on 'The Vampire Diaries' don't seem to be stopping anytime soon. Let's hope these too can keep it profesh!