When Jason was little, his best and only friend was Robin, the Boy Wonder—who existed only in the newspapers and his own mind. Together they had exciting (imaginary) adventures all around Gotham City, helping the Batman take down criminals and bad guys. This was before Jason was the bad guys, though. And even then, he hated being a criminal.
From the time he was around eight onward, Jason had to provide for both himself and his drug-addicted mother, who couldn't support a job anymore due to long-term illness and addiction. He begged on the street, stole and eventually prostituted himself to make ends meet. His experiences left him overwhelmingly distrustful of men, and pathologically hateful and violent toward domestic abusers and sex offenders. He vowed to one day make them all pay, for the horrible things that they did: not to him, but to the others he couldn't protect.
His mother's condition worsened over the next two years, requiring intermittent medical attention, and a bad experience with a pimp finally drove Jason to look for different solutions to their financial problems. He tracked down his biological father, Willis Todd, who was at the time working as a bodyguard and enforcer for Ba Sura-King—a morally bankrupt, Burmese-American industrialist operating out of Gotham City. Known openly to his followers, Sura-King (nicknamed "Sewer King" by his men well out of earshot) kept a mixed group of illegally trafficked Southeast Asian- and Gotham-native children as prisoners at his estate, to serve as domestic laborers and sex slaves. Hoping for a financial incentive, Willis turned Jason over to his boss without a second thought.
Jason was Sewer King's prisoner for the better part of a year, and in that time he quickly became the sadist's favorite chew toy, so to speak, for his bothersome habit of trying to protect the other kids from harm. He was frequently raped and beaten, and, along with the other children, was usually kept in a dark cellar except at night, so that he never saw the sunlight. The children were starved and expected to abide by a strict and often arbitrary set of "house rules," the most important of which was that they could never speak or make any unnecessary sound. Those who disobeyed—again, mainly Jason—were gleefully made into examples for the others, publicly tortured and humiliated for Sura-King's men, or else set loose for the many vicious, trained attack hounds kept on the property to hunt down and brutalize them.
When he was ten, Jason finally managed to escape Sewer King's estate. He immediately sought out his mother, only to find that she had died during his time in captivity. The only thing he could think of left to do was try to rescue the other children, so he began stealing again, with the idea that he might be able to buy back their freedom if he could get enough money. He didn't have much hope, but then, he didn't have much of anything else either.
While trying to jack the tires off the Batmobile itself in Crime Alley, Jason found himself face-to-face with none other than the Caped Crusader, along with his sidekick (now called Nightwing). Jason tried to run, but predictably, he didn't get far. Though he still had problems speaking after a year of forced silence, he managed to communicate to Batman that there was a serious problem at Ba Sura-King's Gotham mansion that demanded immediate attention. At Nightwing's request, Batman deployed the Team to investigate, and they successfully apprehended Sewer King and rescued the remaining children. Willis Todd was killed in the ensuing fight, leaving Jason an orphan.
Jason's stay at Wayne Manor was meant to be temporary, just until Bruce could find him a suitable foster home. However, Jason quickly imprinted on Bruce and belligerently refused to consider any other guardian, threatening to take to the streets again if he didn't get his way. Not wanting to cause the boy any more pain, Bruce finally agreed to keep him at the manor—though he had some serious doubts that his lifestyle as Batman would be conducive to Jason's rehabilitation.
Bruce caught Jason sleeping on the floor or curled up in the Batmobile a handful of times during his first few weeks at the manor. The bed was just too soft to be comfortable, Jason sleepily explained to him, after so many years going without one.
Jason made his initial bid for Robin by stealing Dick's old suit right out of the Batcave, even though it was several sizes too big for him. Nightwing wasn't happy at the prospect of being replaced, despite the fact that Robin wasn't technically "his" anymore, but Bruce thought it might be therapeutic for Jason to have an outlet for his anger and desire to suppress crime. And no one could say that Jason didn't work hard at his training.
For a time, Jason attended therapy sessions with a respected psychiatrist operating out of Arkham, Dr. Harleen Quinzel. He soon went sour on the whole idea, though, after Harleen descended into madness and ran off to join the Joker for a life of crime.
Jason often used the cape of his Robin suit as a way to hide, keeping it fully drawn around himself whenever he could. He didn't like being looked at or touched if he could help it, and had a habit of snapping at anyone who got too close without his permission—except for Bruce, to whom Jason would probably have been permanently attached at the hip, given the choice.
During his second week of patrol, Jason flew off the handle and broke the arm of a man who had been beating a prostitute into unconsciousness in a cheap hotel room. When Batman reacted with anger and threatened to bench Jason from Robin duties, Jason quickly broke down crying and begging, afraid that Bruce was going to throw him back out on the street to fend for himself. It took over a year before Jason finally felt secure in the knowledge that he had a permanent place in his new home, that he was a Wayne now, too. The adoption calmed his fears considerably.
Though Dick and Jason's relationship markedly improved after the first rocky year, they both continued to harbor a great deal of envy towards one another for a long time. Jason envied Dick's natural athleticism, his leadership, his popularity within the superhero community, and the fact that he had come first, both as Robin and Bruce's ward. Dick envied Jason's fearlessness and his outspokenness, and how Batman seemed to let him get away with disrespectful actions Dick would never have dared to try at his age.
Despite his traumatic childhood experiences, Jason seemed to take extremely well to his new life, throwing himself into school and training with all his heart. As Robin, he was almost as unerringly bratty and cheerful as Dick had been, if not as skilled. However, unlike Dick, Jason was flippant at times about following orders, and he also had a violent, unpredictable temper—especially when it came to the types of criminals he loathed most, those who mistreated women and children. He had frequent nightmares and panic attacks, and no one ever really knew what might set him off on a given day...or what might only serve to make him angry.
Jason got along poorly with most of the Team during his tenure as a member, much preferring to work alone with Batman. He only joined in the first place out of a sense of pressure to live up to the expectations of the "Robin" title, wanting to match up to his predecessor. He was even worse at following orders from a squad leader than from Batman. And it was obvious to everyone that stealth wasn't really Jason's strong suit, however much he'd been trained for it.
Jason did get along well with Rocket, though, and the two of them became close in an almost sibling-like manner. Jason didn't approve of her dating and held grudges against all her former boyfriends, including Aqualad and Nightwing. He threw a fit when he first found out Rocket was pregnant with Amistad, fearing she'd been raped, and it took some convincing before he accepted that she hadn't been and wanted to keep the baby.
After his experiences with Sewer King's hounds, Jason had a severe phobia of dogs, even small ones. Wolf's presence at the Cave disturbed him so much that he threatened to "put that fucking mutt down" himself if Superboy didn't keep him at an acceptable distance. Understandably, Superboy and Jason were not particularly good friends after that.
Once, and only once, Jason interrupted Nightwing at his computer. He crawled into Dick's lap and straddled him, wearing the seductive leer he'd perfected at eight years old, purring something about all the things he could do to make the "boring detective work" a little more fun. When Dick shoved Jason violently out of his chair and demanded to know what the hell was going on, Jason lashed out right back, demanding to know in turn why nothing he ever did seemed to impress Dick, the way it did Bruce. No matter what he did, no matter how hard Jason tried at being Robin, he just couldn't make Nightwing happy enough to accept him. Sex was the only other thing Jason was even good at, and it wasn't like he'd have told anyone, he explained, angry and humiliated. Horrified, Dick sent Jason away—but after they'd avoided each other for over a week, he finally sucked up his pride and dragged the younger boy down to the gym at the manor to practice some of the trickier acrobatic flips he knew Jason didn't have quite right yet. Platonically, Nightwing emphasized firmly, and Jason looked more than a little relieved.
Out of all the Justice League members besides Batman, Jason had the most respect for Black Canary. Once, during a particularly bad row with Batman, he half-seriously asked Dinah if he could be her sidekick instead of Bruce's. She turned him down, but the offer touched her deeply nonetheless.
For all that they fought, Jason was obsessive about Bruce. He idolized him and was willing to do anything to get his attention, positive or negative. Sometimes he went out of his way to test the limits of Batman's patience, waiting in fear for the day when Bruce would finally snap and begin to mistreat him the way other adults had in the past; or worse, simply give up on him. However, that day never came, and once Jason accepted that Bruce cared about him beyond his usefulness as Robin—and had no interest in using him for sex—his behavior began to noticeably improve.
Jason was more than happy, ecstatic even, to have Bruce as his new father. And in time, he and Dick eventually grew to genuinely love one another as brothers. However, despite how badly his parents had failed him in the past, and how very much he loved (loved loved loved pleasedon'teverletmegopleasegodplease) his new family, Jason still loved his parents in his heart and wished they were alive.
So when Jason found out that his mother, Catherine, had never actually been related to him by blood at all, and that his birth mother was still alive, living out in Ethiopia...he jumped on the chance to be reunited with another part of his lost family. Despite Bruce's reservations, Jason went to find the woman who had given birth to him, told her everything about who he was and what he had made of his life, how he hoped he had been able to make her proud. He told her about Robin.
And, just as Willis Todd had done years before, Sheila Haywood sold her son down the river without the slightest bit of hesitation or remorse—this time, to Batman's worst nemesis, the Joker himself.
Jason still died trying to save her from the bomb.