JayDick

JayDick is the family ship between Dick Grayson and Jason Todd from the DC Comics fandom.

Canon
Both Dick Grayson and Jason Todd were adopted by Bruce Wayne a few years apart, Jason inheriting Dick's former title Robin when he did so. Jason typically tried to prove himself, while Dick tried to be more of an older brother.

Films
The Autumn of Terra set Batman film, Gotham by Gaslight features Dick and Jason as orphan children beside Tim, who are forced to steal for Big Bill Dusk. Because neither of them have parents and have had much taken away from them, the boys became each other's family. Dick being the oldest has him looking out for Jason, even though Jason had first appeared as the leader of the three when they tried to attack an elderly couple for money, while Dick reminds Jason to not use their names in front of their targets. They have heard rumours of Batman but didn't believe in them, as the two tell Tim that he is only thing that grownups make up to ensure that kids like them behave. Until the night they come face to face with the Batman himself, who tells the three to return to their mothers. Dick and Jason tell him that they don't parents and are each other's family, while taking back from Gotham as they know that Big Bill will only come after them if they were to run away from him. This gets Batman to give the boys a chance to get a head start when they go to seek refuge at a church that takes in orphans. When Alfred caught Jason trying to steal from one of the carriages Dick asks him to not turn Jason over to the police, before scolding Jason for going against what Sister Lesly had been trying to teach them at her funerial. Because Alfred showed them kindness by giving them food, Dick, Jason and Tim agree to deliver an unknown package. Not knowing that is in it has Jason wanting to steal it, along with the cart and the horse, but Dick was on Tim's to do what they were asked. Along with reminding Jason that he is one of the three who can read. After they help Alfred and Tim save Batman and Salina, Dick and Jason tell them that they shouldn't be sad for the burning fair and that all of them can create something that is real and better.

Batman Ninja has Nightwing and Red Hood being sent back to the feudal era of antient Japan beside the other Robins and Gotham City's top criminals, before Batman joins them two years later. During those two years Nightwing, Red Hood and the other two Robins get taken in by the Bat Clan who teach them the ways of the Ninja and how to survive in their timeline. Red Hood being the loner that he is has him serving as a scout who keeps an eye on Gotham's criminals who have each made themselves feudal lords, while Nightwing remains with the others, since their youngest Robin has befriended a monkey who has away to find the messages that are sent to them. Sometime after Batman gets reunited with his Robins and has recovered from their battle with Joker, Red Hood regroups with Nightwing and the others as they prepare for their epic battle with Gotham's criminals, so they can get their hands on the machine that will send them all home.

The relationship between Jason and Dick depends on the choices that viewers make in the interaction movie version of Under the Red Hood, Batman: Death in the Family. In the versions that have Bruce die in Jason's place, Dick does what he can to be there for Jason as he recovers from his injures while using the Bat computer to help them find Joker as his way to work through their loss. Jason had promised Dick and the others that they'll bring in Joker the right way together, while Jason secretly wants to kill Joker alone. Jason's monolog has him calling Dick a big brother and had became annoyed by Dick telling him Batman stories over and over again. With Bruce gone Dick becomes Batman in his place while Jason continues on as Robin. The second part of this version also depends on what Jason does after he kills the Joker at a dinner, allows himself to be arrested for what he did or becomes a murderer version of Red Robin as he makes it his mission to kill all criminals. Dick as Batman tries to stop Red Robin knowing that he has to be stopped. The ending of this version also depends on what Red Robin does next, in the one that has he getting defeated by Two-Face and begins to regret what he did Dick welcomes him back as Jason tries to atone for what he did as Red Robin. The other version of Red Robin's battle with Two-Face has him meeting Tim Drake who becomes Bat Kid, while Dick makes sure that the redeemed Red Robin doesn't stray from the path Bruce set the two of them on again. While in the versions that does have Jason becoming Red Hood in an attempt to lore Joker out, Dick tries to arrest Jason for what he did as Red Hood, even when one of the option endings has Jason not killing Joker and needed the support of his family when he realises that he broke his promise to Batman. Dick eventually welcomes Jason back in the version that Jason deciding to save Bruce after he learns that Talia al Ghul had brought a broken minded Batman from the dead, and later brings Bruce back to the Bat family so they can all look for ways to cure him. Jason decides to let Dick do the field work while he takes time off to truly recover after he burns his Red Hood gear and clothes. In versions that have both Jason and Bruce surviving the blast, an angry recovering Jason sees Dick as a victim of Bruce's mummy-daddy issues who is giving him false smiles to find his true pity thoughts of him and no longer wanted to be part of a family, while Dick was only happy that Jason was alive, as all those negative thoughts were in Jason's head.

Fanon
The two are adopted brothers. Their blue and red color scheme and how they act with one another through their brothers-like bond has inspired a small group of fans to compare the two with Leonardo and Raphael from Teenage Mutant Ninja Turtles.

Fanworks of the pairing have appeared on YouTube, Archive of Our Own, Tumblr, DeviantART, Wattpad, and Fanfiction.net. Based on works posted at Ao3, it is the most popular pairing for both of these characters and is particularly popular in the DC comics fandom. This pairing also appears in Teen Titans and Young Justice fandoms. It is also the second most popular pairing in the live actions Titans TV series fandom, despite the two's limited interactions.

Trivia

 * The two are set to appear in Gotham Knights.