Of all the Titans she has come to know, Robin is the one she is least antagonistic to. Since the day their team formed he always watched out for her, and in return she began to open up to him more than the others. It started with simple respect in "Nevermore" despite not knowing about her, he knew well enough to tell Beast Boy to apologize for accidentally antagonizing her after her first demonic episode on Dr. Light. He also respected her privacy well enough to try to stop Starfire from going to Raven's room. Raven in turn was at first hesitant to be his friend. In "Go" she said if the team knew who she really was, they wouldn't want them around. To which Robin replies "I know enough." She eventually warmed up to him to the point where in "Aftershock Part 2", she knew to use a forcefield around the team when Robin disabled the Slade Bots with an EMP; just by hearing the words "RAVEN NOW!!!" In "Haunted" Raven entered Robin's mind to save his sanity from Slade. While in there, she caught glimpses of Robin's past including his time with Batman, and the death of his parents. This event caused a special bond between them as mentioned in "Birthmark." During the events of "Birthmark" she stopped time in order to stop Slade from killing her teammates, the only one she left unfrozen was Robin so he could try to protect her. During that time she was about to confess a horrible truth about her past to him that wasn't fully revealed until "Prophecy". That truth being she was the daughter of Trigon: an evil demon bent on destroying Earth using her as a portal. Despite the confession Robin's opinion of her since "Go" hasn't changed. He even spearheaded a plan with the team to put her in a safety room in "The End Part 1" despite her protests. This showed that both of them was willing to protect one and other. From Robin willing to protect her from Slade and Trigon; to Raven transferring her powers to him and the team in order to give them a fighing chance. In "The End Part 2 and 3" after Raven was hinted to be alive during Trigon's reign, Robin was more than willing to go down to the bowels of the destroyed earth to rescue her.
Fans of the show often debated whether or not Robin and Raven's willingness to stick their necks out for each other was due to a romantic interest to one and other. There have been things they have in common to further hint to it.
- Both have bird themed names, Robin and Raven respectivly.
- Both have troubled pasts which strengthened their bond with one and other.
- Both don't want to live in the shadows of the father's in their lives.
- Both use darkness and shadow to their combative advantage.
That being said some of the episodes in season 4 have teased with it. In "Haunted" Robin let Raven see not only into his mind, but through his own eyes when he tried to prove Slade was back. In "Birthmark" Robin was the only one freed from the Time Freeze that Raven put on the world. Robin was also the only one she opened up to about her past. In "The End Part 1." They both shared a moment to watch the sunrise together. When Raven transferred her powers to the team, she told Robin specifically "Be safe." In "Part 2 and 3" Robin went down to the bowels of the destroyed earth to find her and despite not remembering him, she trusted him well enough to take her back to the surface. After Trigon's defeat, the first thing Raven did was hug Robin.
While the above examples hint at romance, other fans often thought that their relationship was that of a surrogate brother and sister. In "The Beast Within" Robin went as far as threatening Beast Boy under the thought that Raven's injuries were his cause. Sometimes he acts like a surroagate parent to Raven such as in "Titan Rising" When he deliberately makes Raven and Terra work together, knowing full well they don't trust each other. As well as "Nevermore" When he acts like the father respectively to Starfire acting like the mother, by trying to stop her from disturbing Raven after she locked herself in her room. However like siblings they tend to get on each others nerves sometimes. In "How Long is Forever." they were arguing over him turning the music up loud while she was reading. Regardless, Raven and Robin treat each other like family as well as the rest of the team. As stated in "The End." where she says "I was protected by the monks of Azarath, I was raised by my friends!!!"