Serena van der Woodsen vs. Summer Roberts

Today is both Blake Lively and Rachel Bilson's birthday. The stylish starlets share more than the day they were born, though. On Gossip Girl and The O.C. — which sometimes seem like the same show just shot on different coasts — the two entertain love interests who have quite a bit in common. From the dorky outsider to the bad boy, see the types of men both Serena van der Woodsen and Summer Roberts have dated.