The latest episode of DC Universe's Titans ("Together", watch it here) is a special one for fans of one of the greatest love stories in the history of DC Comics -- that of former Robin Dick Grayson and the alien warrior princess Starfire, a.k.a. Kory Anders. The two met when Raven brought together various teenage heroes to form the New Teen Titans (read the team's early adventures here).
Starfire, who was really princess Koriand'r of Tamaran, had escaped slavery from the Citadel Empire and fled to Earth. Upon meeting Robin and fighting alongside him in battle, she passionately kissed him, because Tamaranians absorb language through physical contact (also, she just thought he was handsome). Even the straight-laced Dick Grayson couldn't deny the instant attraction between them. That first kiss was the beginning of a long romance, but one fraught with obstacles.
As the New Titans went on many adventures together, Robin and Starfire grew closer, and eventually they started formally dating. Robin often got frustrated with Starfire, as her emotional nature was often too much for him to handle. She would often go into her Tamaranian warrior mode, and Dick would have to hold her back from killing criminals more than once. Meanwhile, Starfire would get equally frustrated at Dick's hesitation to give in to his emotions and instead suppress them. Despite these differences, Robin and Starfire were deeply in love, and the two young heroes simply couldn't keep their hands off of each other.
The two hit the first major hurdle in their relationship when Starfire was called back home to the planet Tamaran, where her father ordered her to enter into a political marriage with a young man named Karras, the son of a high-ranking Tamaranian, whom she had never met before. The union was entirely a marriage of state, and Koriand'r was not expected to give up her relationship with Dick, who was now Nightwing. But the conservative Grayson simply couldn't stand being the "kept man" of a married woman, and left his beloved behind on Tamaran. Starfire did her best to be happily married to Karras, but she left her new husband behind and went back to Earth, hoping to save her relationship with Nightwing.
Eventually, Nightwing and Starfire resumed their romantic relationship, despite Nightwing's misgivings about Starfire's married status. When Karras died out in space, this left Dick and Kory free to finally wed. The shapeshifter Mirage, who was a new member of the Titans, tricked Nightwing into making him think she was Starfire, and seduced him. When the real Starfire found out about this, she was furious that Nightwing couldn't see through Mirage's illusions, but Dick hoped to make it up to her by proposing marriage, to which Koriand'r said yes.
All their fellow Titans, as well as other Super-Heroes, gathered for the big wedding day, but before the priest could pronounce them Husband and Wife, he was murdered by Dick and Kory's former teammate Raven, who had once again been corrupted by her demonic father's influence. It seemed that no matter what, these two young heroes could never catch a break.
After Raven was defeated, and returned to her non-evil self again, Starfire decided to return to her homeworld of Tamaran, thus breaking up the Nightwing and Starfire romance for a good long while. Eventually, the Titans reformed once more, and Starfire returned to Earth. She and Dick acknowledged that their feelings for one another had never really gone away, but they didn't actually start seeing each other romantically again. During this time, Dick started dating former Batgirl Barbara Gordon, on whom he'd had a crush before he meet Starfire.
Starfire would go back and forth between Earth and Tamaran, often joining up with the Titans for a while, and then heading back to the stars, where she joined the intergalactic team the R.E.B.E.L.S. for a time. Upon Kory's return to Earth, Nightwing and Starfire would resume their physical relationship, but the emotional one never fully recovered from the disaster of their wedding that never was. Although Starfire was still very much in love with Nightwing, as the years went on it was clear his feelings for her had changed. Eventually, the two decided just to be friends, but the physical closeness of being on the same team was too hard for Kory to bear, and she left the Titans.
When the DC Universe was reimagined after the events of 2011's Flashpoint, Starfire appeared as a member of Red Hood's team the Outlaws. Although she was in a physical relationship with the Red Hood, who had an uncanny resemblance to Dick and had been his replacement as Robin, she alluded to the fact that she and Dick Grayson had been in a relationship together at one time as well, but that things had not worked out for undisclosed reasons. It's unknown if Nightwing and Starfire were ever even teammates in this new reality.
It remains to be seen if Dick Grayson and Princess Koriand'r, two star-crossed lovers if ever there were, will some day find a way back to each other again. Although Dick and Kory are quite literally "from two different worlds," few heroic couples have had more chemistry than Nightwing and Starfire.