Although, it did seem like it could be the case when they started dating in real life at the beginning of the show... but that relationship didn't last two seasons of the show!
The two broke up halfway through the season, and kept it a total secret from the others.
In a new interview with Vanity Fair, Blake opened up about her romance with Penn. Although their private lives were all over the headlines at the time, they tried their best to keep their relationship a secret...
"I remember there was one point where we were just afraid of how our personal lives overlapping our work life could be perceived by our bosses," Blake said. "[But then] we were like, ‘Oh no, that’s exactly what they want.’ They wanted us all to date. They wanted us all to wear the same clothes that we’re wearing on the show. They wanted that, because then it fed their whole narrative. People could buy into this world."
“At the time, I was wearing the same clothes and doing fashion shoots, and dating the same person that my character was dating — or sometimes that person [Dan] was my brother, you never know with Serena — and because of that, what people were projecting onto me was that I was Serena," she continued. "We look the same, and we acted the same as far as they could tell, because I wasn’t doing anything but that show. If [Penn and I] were photographed walking down the street, they didn’t know if it was a paparazzi shot or if it was a shot from the show."
The couple dated for three years before splitting up in 2010. They didn't want their break up to effect their professional lives at all, so they kept it hush hush.
The shocking thing was, I found out on the set of the Season Two finale that Blake and Penn had broken up months before,” Gossip Girl co-producer and writer Joshua Safran told Vanity Fair. “They kept the breakup hidden from the crew, which you could never do now. I don’t even know how they did it. They kept it from everybody, which is a testament to how good they are as actors. Because they did not want their personal drama to relate to the show.”
The next four seasons the pair 'dated' on the show. Imagine having to do that with an ex?!