Love on Set: 13 of TV's Hottest Co-Star Couples

Gossip Girl co-stars Blake Lively (Serena) and Penn Badgley (Dan), who went from lovers to step-siblings on The CW soap, dated for almost three years while filming the show. After calling it quits in October 2010, Blake spent the summer hooking up with King of the A-Listers Leo DiCaprio, and Penn has moved on to X-Men: First Class star Zoe Kravitz, daughter of Lenny Kravitz and Lisa Bonet.

After the split, Blake dished to Glamour (via Us Weekly), "Every relationship you have, you're learning and growing and taking something from that. So for me, it's never been too dramatic of a thing when something ends."