BIOGRAPHY
Adrian Corbo and his older half-brother, Jared, were born to the same mother. For unknown 
reasons, the boys were sent to an orphanage known as Hull House in Ontario. It's possible their mother had died or was incapacitated, or that she was pressured to send the boys there by Department H. The powerful government department had ties to the facility and used it for watching over so-called “legacies,” children of super-powered beings, as part of the Super Hero Youth Acceleration Program. The brothers were not particularly fond of their time at the orphanage, thinking of it more of a prison than home. [Alpha Flight (2nd series) #3]
For Adrian, it was more than just a prison. It was hell, as he was tormented and possibly abused by someone. While little is known about this torment, it is possible that Adrian knew his abuser, although the abuser appeared to him as a monster who spoke in a strange manner. [Alpha Flight (2nd series) #5]
However, one of the volunteers at the orphanage, a certain Eugene Judd, tried to make sure the children had a normal upbringing, and played basketball with Adrian and Jared. [Alpha Flight In the Beginning #minus1] Adrian was also given the nickname “Flex” when Jared asked him to flex his muscles. However, this was meant to be ironic, as he was the scrawniest kid at the orphanage and the other kids found the nickname funny. [Alpha Flight (2nd series) #4]
At some point both Adrian and Jared, along with another Hull House orphan, Arlette Truffaut, all developed mutant powers. When Department H was restarted after several years of being inactive, a new Alpha Flight team was formed, of which Adrian was a member. His codename was Flex, thanks to his ability to transform his limbs into razor-sharp blades of organic steel, as well as a throwback to his childhood nickname. Adrian was young, one of the youngest members of Alpha Flight ever, if not the youngest, and appeared nervous and hesitant from the very first moment. At a training session, Adrian stood back from the other members of the team, not wanting to fight them. However, when he accidentally backed into Sasquatch, he was instinctively frightened and turned his hand into a large blade, knocking Sasquatch back from him.
It's not clear whether Adrian remembered Eugene Judd – Puck – from his time at Hull House, but he listened to Puck when the Alphan tried to give him some advice about fighting and warned him that their enemies would not hold back.
Although the new recruits were all being trained by veteran Alphans, Alpha Flight itself was under the administration of General Clark. Although Heather Hudson told the general that the recruits, Adrian among them, were not ready for missions, it was not long before they were needed to stop the new terrorist group known as the Zodiac. Adrian was very nervous about heading into the mission, but the experienced Alpha Flight member Maidson Jeffries offered to watch Adrian's back, if Adrian would do the same for him. Unfortunately, the mission was a disaster and, when 
Jared (known as Radius) knocked the Zodiac member Taurus towards Adrian, he instinctively turned his hand into a large shard of metal and was unable to retract it before Taurus was impaled on it. Radius then distracted the already shell-shocked Adrian, who was supposed to cover Jeffries, enabling the Zodiac to kidnap Jeffries and escape. [Alpha Flight (2nd series) #1]
When Department H created synthetic doubles of Alpha Flight's longtime enemy the Master of the World and set them loose upon the new Alpha Flight, Flex was fortunate enough to have Puck encourage him and give him advice during the encounter. Unfortunately, Flex's own brother, Radius, was not so encouraging and picked on his brother at every opportunity he could. [Alpha Flight (2nd series) #2]
When the senior members of the new Alpha Flight went to investigate strange goings on near Hull House where the younger members of the team grew up, Flex found himself remaining at Department H with Radius, who wanted to explore the facility. Flex reluctantly accompanied his brother and they came across the Helios Project, where experiments were being conducted on the former X-Man known as Sunfire. After busting Sunfire out of Department H, Flex tagged along when Radius, Murmur and Sunfire and stole a Department H jeep and went for a ride, ending up at a diner. By an unfortunate coincidence, the diner was under the control of the psychic Mesmero, who had encountered Alpha Flight many years ago. The inexperienced heroes were quickly put under Mesmero's control and, when the senior Alphans arrived to find their missing teammates, a fight ensued.
Mesmero eventually lost control of the new Alphans, but found himself with the experienced Alpha Flight members at his disposal, so the fight continued, with the roles reversed. Flex found this particularly difficult and, after being hit in the face by Puck, fled and hid in the diner’s kitchen. When he was eventually found by Murmur, he told her through his tears that he hated this, and wanted to quit. When Murmur wiped away Flex's tears, however, her skin touching his, she used her power to give him courage and the reinvigorated Flex leapt back into the battle. Unfortunately, Murmur's influence faded quickly and, when Puck began to chase him, Flex again became scared and had a flashback about being tormented as a child at Hull House. Frustrated, Flex attacked Puck, only to discover Puck was no longer under the control of Mesmero, who was defeated shortly after. [Alpha Flight (2nd series) #3-5]
Adrian held over a lot of the trauma from his childhood at Hull House, so much so that he was even nervous to leave his quarters at Department H during the nighttime to use the bathroom. However, one night, he had to use the facilities and crept out into the hallway – where he came face-to-face with a strange, glowing energy. Frightened, Adrian ran but the energy only followed him. Adrian did make it to the men's room, where he hid in a shower cubicle for the rest of the night. When he was discovered by his brother the next morning, Adrian tried to explain to Jared what had happened, but Jared only teased him.
During a training session, he again mentioned the energy creature but this time Heather Hudson believed him, as she had seen it too. To distract himself from the terrors of Department H's corridors, Adrian began an online search to try to find his and Jared's respective fathers. After leaving his quarters to go to dinner with Jared and Arlette, the three young Alphans came across the energy creature. This time, they gave it chase but, when they reached a corridor with a dead-end, the strange energy creature had vanished. They encountered the creature one more time that night, but never solved the mystery of what it was. [Alpha Flight (2nd series) #7]
Department H was full of mysteries at this time. In addition to the strange energy creature, the heroes of Alpha Flight were also having their memories tampered with. As part of that, they were told that Madison Jeffries was killed by Wolverine. Flex accompanied the rest of Alpha Flight on an assignment to retrieve Wolverine, which led to an encounter with the X-Men. Flex didn't want to fight and his fear was apparent even to Cannonball, as the X-Men blasted towards him. While their teammates fought around them, the two stopped and talked about matters, at which point Flex learned that Wolverine couldn't have killed Madison Jeffries, as he had been with the X-Men. The two young heroes then ended the battle by explaining this to their respective teammates. [Alpha Flight (2nd series) #9 / Uncanny X-Men (1st series) #355]
Shortly after, Flex discovered that his brother's father was the mutant criminal Unus the Untouchable. This happened just before he joined his teammates on a mission in the reality known as the Microverse, where he and Alpha Flight assisted the renegade heroes known as the Micronauts overthrow a tyrannical leader. [Alpha Flight (2nd series) #10-11]
Back on Earth, Flex and his teammates had their own tyrant to deal with – namely their administrator, General Clarke, and the secrets going on at Department H. However, upon returning to their home, they found it overrun by their enemies the Zodiac, who were in search of a mysterious weapon known as the Nth Projector. During the chaos, Flex noticed that among the Zodaic was Taurus, whom he had thought he had previously killed. Before he was forced into a rematch, Flex was essentially removed from the battle when he accompanied the mysterious Alphan known as Manbot to the even more mysterious 13th Floor. There, Flex was given a device 
that enabled him to see all around Department H, so he could communicate with his teammates and assist them against the Zodiac. Not only did Alpha Flight prevail, but they also learned that Jeffries was still alive, although seemingly brainwashed and under the Zodiac's control. [Alpha Flight (2nd series) #12]
A new era for Alpha Flight began shortly after, with a new administrator who planned to clean house and expose all of Department H's terrible secrets. Flex and Alpha Flight welcomed this, following the harrowing experiences they had recently endured. [Alpha Flight (2nd series) #14]
Flex accompanied Alpha Flight on their first mission under the new regime – to investigate the strange goings-on at the town of White Cross in Newfoundland. This led to an encounter with the villain known as the Brass Bishop, who had the citizens of White Cross under his control. Just as Flex found himself overwhelmed while keeping the zombie-like civilians at bay, he was surprised 
at how his powers suddenly expanded his entire body, knocking the civilians back. Not only that, but Flex prevented his teammates from becoming trapped and so they were able to carry on with the mission, defeating the Brass Bishop and freeing the civilians from his control. [Alpha Flight (2nd series) #15-16]
Flex soon met another young mutant who had been held captive at Department H after being brought there from Hull House, Lilli Stephens, whose codename was Ghost Girl. The two literally bumped into each other in the corridors of Department H, and it was love at first sight.
Further developments in Adrian's life followed when he discovered the identity of his father. Unfortunately, every time he tried to talk to somebody about it, he was interrupted by other goings-on at Department H. In fact, the team was soon caught up in a complex battle with surviving members of the original Alpha Flight and a deadly new Weapon X. Both Alpha Flight teams eventually started working together to defeat the new Weapon X. [Alpha Flight (2nd series) #18-20]
In the aftermath, Department H decided to restructure Alpha Flight, bringing former members back into the fold and demoting Flex and the other younger members (including his brother and Ghost Girl) to a new Beta Flight training team. [Wolverine (2nd series) #142] In unrevealed circumstances, that Beta Flight team apparently went their separate ways, with two of the team de-powered following M-Day and another killed in action. Although Alpha Flight has been restructured several times since, Flex has never been a part of any subsequent team. Given his reluctance to be a part of the team in the first place, it's entirely possible that he has opted to live a quiet life outside of the super hero life, maybe even with Ghost Girl at his side.
[NOTE: Originally, writer Steve T Seagle intended for Flex's father to be Wolverine but, with the series' cancellation, he was unable to formally incorporate that into the stories.]