Seth Rogers is six years old when he comes home from school in tears. "They made fun of my braces," he sniffles, trying too hard to be brave. Steve holds him tight and tells him it's just because they don't understand, but the look in his eyes says he's minutes away from an agitated phone call to Seth's teacher. Tony sees the gathering storm and takes Seth's hand.

"Hey buddy," he says, "I've got an idea. These old braces are kind of boring, I'll bet we could fix them up a bit, what do you say? We'll get you some chrome trim, spinning rims… sound okay?"

Seth rubs the back of his hand across his eyes and gives a grudging nod.

"Great," Tony says, "awesome, cool. Come on, I'll show you my workshop. You're gonna love it, we've got all the toys. Your uncle Banner spends all his time down there," he chatters as he leads Seth away, "you couldn't pay him to leave. I mean that's you, YOU couldn't pay him to leave, I pay him to stay… I think he lends to the décor…." True to form, Tony doesn't shut up, but he earns a smile from Steve who recognizes his technique. This is how Tony makes friends.

The next day, Seth goes to school with bright green and chrome braces. They are ten times lighter than the ones he was wearing before and they move like oiled silk. He barely feels like he's wearing anything at all, and every joint has holographic spinning rims exactly as promised, and he awes his class telling them they were made by Iron Man just for him. His teacher, who was given a very thorough talking-to the previous day, keeps a closer eye on him and while the teasing doesn't stop most of it loses its strength. It's hard to mock something created personally by Tony Stark.

Seth is nine and wincing as one of his Uncle's security men flops onto the mat. He's a foot taller than Clint Barton and twice as wide but that sort of thing has never bothered Clint. Skinny, anemic, boney Seth Rogers sees hope in those effortless movements and he tugs on Clint's belt.

"Mr. Barton?" he says shyly, cheeks burning - he knows what Hawkeye sees in him, a scrawny slip of a boy with twisted legs who'll probably never outgrow the need for those braces, who'd be laid out by an asthma attack after one lap around the gym. "Can you show me how to do that?"

Clint glances around... Captain America is nowhere in sight. "Sure," he tells Seth, and kneels down so he's on his level. "The first thing you should know is that Aikido is not about force. It's about using your opponent's strength, not your own."

Seth likes the sound of that. He isn't very strong. He listens to what Barton tells him and later, in the privacy of his bedroom, he practices over and over.

Seth is twelve years old and has blown out his fifth circuit trying to add another power source to his braces. Their mechanized movement assistance is minimal – normally they need very little power because Tony designed them to be efficient, but he has plans, big ones, and they require some upgrades. Last week he and Tony sat together for five hours straight on a Saturday night while Tony showed him all the intricacies of the internal structure of his Iron Man boots. It's like being handed the keys to the kingdom. He told Tony that for his science fair project he wanted to write a software program to replicate a basic running movement with the capacity to adjust for the mass of the person using it, to slow down and speed up based on simple controls, to do all this without putting its user in danger.

Tony knows damn well that Seth washed out of the track and field program – asthma again. He tells Seth that technically, using this program would constitute cheating, but Seth doesn't care because it's not about competition anymore – he just wants to run.

Seth is fifteen and his father and his uncles are at it again. Bruce and Tony stand together on his side and he appreciates it, but he wishes they understood he'd rather take the scolding from his father than listen to them fight. They fight over lots of things, not just him, and some of those fights make him afraid for the future of their mismatched team.

It's their home, so Tony has to leave eventually. He probably tells Steve not to be so hard on the kid because lately he's been saying that a lot. Steve comes in, saddened and weary, carrying the print-outs from the doctor's office in his hands.

"This isn't about you trying to work hard," he begins, and Seth can see how much it hurts him to explain it, like it's hurt him every day of every year of his life. "I understand what you're doing, believe me. I respect it, Seth, and I respect you. But these measures you're taking are dangerous. They could have long-term effects on your health," he explains, fingering the paper sheets, bending them. "Things like equipment and exercise machines and muscle-toners and energy drinks, these are all tools and some of them work and some of them don't but any one of them can hurt you when you use them so… obsessively. And this could have been a lot worse… the doctor said these things can cause permanent nerve damage. And there's no guarantee they even work." His eyes come to rest on the colorful, glossy cardboard box sitting beside Seth's bed. Its printed surface promises results in only 30 days, painless, cutting edge. Children under eighteen can't even buy it but Steve refuses to worry about where it came from because his son has no shortage of willing accomplices. "I know what it feels like to be where you are," he says. "I was there. But you've got to stop trying to be me, Seth. Be satisfied with you."

"I know, Dad." They hug. They make up. Steve leaves him alone for a bit and Seth climbs out the window. His dad thinks this is about wanting to be Captain America, but he's wrong. He doesn't know what it means to Seth to use his own designs, his own mobility aids, to sprint between the trees and drink in the wind. He doesn't know the delicately-balanced relief of having to rely on his home-made infuser to keep a thin stream of medicine flowing into his lungs so that he can breathe in time with his pounding heart. He doesn't know the pain in his ribcage of this kind of exertion, not anymore – all pains are lessened for him, but Seth is willing to hurt to do these things because it's HIM that's doing them.

He can be more. He can do more. He knows it. And he's not going to stop.

Seth is eighteen and he is graduating with honors. It's not fair really – he has the world's best tutors. His AP classes bring his GPA above a 4.0 and he barely has to strain because for his entire life he has eaten physics, breathed advanced robotics, rolled gleefully in chemistry and gotten drunk on mathematics. And military history, because his dad tries to talk about some things but Seth wants to understand. He wants something else too – he wants the knowledge base. Steve excels in strategy and tactics. Seth knows he'll never match him, but he is desperate to impress him.

He applies to several colleges, including West Point – he fails the physical, but unlike his father he doesn't try again. Military experience would have been beneficial for what he has in mind but it's not essential.

His graduation party is a quiet, personal affair. He and the misfits he's befriended through high school get together and play Call of Duty all night long. They drink a little beer – it's a controlled environment – and eat a lot of Cheetos. The next day they are all driving up to Niagra Falls and he's supposed to be going with them. They've promised to cover for him. Not even Bruce knows the truth.

The day after graduation Seth shows up on the Young Avengers doorstep. They are not the military – after a brief, almost cursory interview, they admit him with open arms. So far it's a secret. None of them are supposed to know his true identity, but he thinks maybe some of them suspect. It doesn't matter, though – they all know what it's like to pursue a dream despite the objections of their guardians and he's a legal adult anyway. They won't tell.

Two weeks after graduation, Seth is swallowing painkillers and trying to repair his exo-suit. Kang the Conqueror led a small army of predator robots into the heart of the city to challenge his family and his family wiped the floor with him, with the help of the Young Avengers and some of New York's independent heroes. The robots were future-tech - with his own team's help he kept two of them, secreting them away in the Young Avengers' vault to investigate later. His exo-suit took one hell of a beating. Seth thinks he left half of it on the street but he can't worry about it. If he has to rebuild it, he will - he's done it before. By comparison he took much less of a beating, but he still hurts - the suit leaves him with muscle spasms and bone-deep pain. It's miserable but he won't give it up. He knows how to handle pain.

Tony comes in without knocking. Seth has a moment of pure panic. He grabs his ripped chest-piece and looks for a place to hide it, but it's too late... he's been caught. Tony raises a perfectly sculpted eyebrow and shows Seth what he was holding behind his back. It's one of Seth's gauntlets, crushed and torn off by the predator robot that almost shattered his hand.

"You know, I was wondering how someone got ahold of Stark Industries R&D Tech," he says easily, "guess I should have known better than to ask." He tosses the gauntlet onto Seth's desk and Seth winces.

"Uncle Tony," he begins helplessly. "I can explain."

Tony blinks. "What's to explain? You're Exo. I gave you the tools, kid, you think I don't recognize my own handiwork?" He leans on Seth's desk, half-sitting, talking with his hands. "What I want to know is, why didn't you tell me? Come on, I thought we were tight. I have to find out this way?"

"I didn't want it getting back to Dad," Seth confessed. "You know what he'd do. I'm begging you..."

"Begging' is a little strong..."

"... Don't tell him," Seth pleads, abandoning his dignity in the face of family. "He'll do whatever it takes to make me stop. He's Captain America. If he black-lists me..."

"It won't be the end of your life, trust me." Tony shakes his head dismissively. "You overestimate your dad's reputation a little. He's not everything he's cracked up to be. I know." Tony has his phone out and is fiddling with it. "Kid, if I didn't trust you to have the tools I would never have given them to you. You've got a hell of a brain and you have your mom to thank for that but your dad shines through bright and clear in you. I see more of him every day. I trust Steve Rogers with my life. I'd trust him with a suit if he needed one. So I trust you. And I'm not going to tell your dad," he adds, shoving his hands and his phone in his pockets. "But you should." Serious now, he catches Seth's eyes. The implant in his chest thrums softly, reminding Seth that Tony understands the vulnerability of being only too human. He's not going to take Seth's work away from him.

"That's my pep talk," Tony says, and pats Seth on the shoulder. "Okay? Talk to your Dad. He's a relic from a bygone age and he acts like my grandma..." Tony makes a dismissive gesture. "He's your Dad. Don't make him find out the hard way, that's all I'm saying."

And Tony is gone.

Seth is twenty and his luck has run out. He lies on his back on an alien planet drowning in perfectly breathable air. He knows of no greater honor than to stand beside his father and fight Thanos, the Mad Titan, a mass murderer whose crimes spanned galaxies, but honor isn't going to save him. He's going to die for the lack of an inhaler.

His respiratory assistance system is one of the best-protected internal systems in his suit but he got unlucky - a shot from one of Thanos' minions, just a minion with a blaster pistol, nothing special, managed to tag him and blow out his suit's supply of bronchodilators. The medicine drips into the soil of a world Seth's never seen or heard of, the world he's going to die on if he doesn't figure out how to breathe. He knows he's writhing like a fish out of water and he feels like a child again, vulnerable, at the mercy of all his body's failings.

He wishes for his father and then his father is there, suit torn, bloodied and soot-stained, but real as the crimson sky. He sets his shield beside Seth and reaches out for him. "Exo? Son? Are you all right?" 'Son' is just comforting drivel - Steve still doesn't know. Somehow Seth never got around to telling him the truth and now he wishes he didn't waste so much time.

"Can't... breathe..." he wheezes, and his voice modulator protects his identity, like the black-haired wig attached to his helmet, like the padding in the suit that makes him look bulkier than he is. "Iron... man..."

"Communications went out when Thanos released that blast wave. What can I do?" Steve is so earnest, so honest, so unflappable. He's acting calm because he's trying to keep Seth calm; Seth has seen it his whole life and now it makes him want to laugh because the things his father doesn't know could fill a book and he hasn't been carrying Seth's inhalers around for five years. Tony has one because Tony knows Seth's secret, but apparently Tony is unreachable. "Son," he says and squeezes Seth's gauntlet. A little of the pressure translates and Seth blinks back tears. "I need you to focus. What can I do?" He looks down. "Are you having an asthma attack?" Of course he would recognize it - Steve had asthma once. Seth has had it all his life.

Seth has to nod. His vision is going gray. He can't get enough air. And then his father is moving him, lifting his upper body, wrapping his arms around him. "It's all right," he says into Seth's ear. "My son has asthma. Just try to stay calm. I'll talk you through it... just relax and listen to my voice. You're going to be all right." They've done this dance before. Usually it's unnecessary because Seth has his inhaler on him, but shit happens in twenty years. "Do you have an air filtration system?" Steve is asking. "You need to set it for oxygen saturation. I can do it if you let me access the controls."

Steve needs to be shown very little - this technology is familiar to him and once Seth pops open the manual control panel for the suit's respiratory filtration system he very quickly makes the necessary adjustments. He keeps talking all the while, and Seth calms down... not because he's no longer dying, but because if he is dying then at least his Dad is here. He is not alone. He stood as a hero and died fighting alongside some of the greatest men and women of his species, and he's okay with that. It's a good way to go. He drifts off listening to his father's voice and he doesn't see the red and gold streak across the sky. He doesn't feel it when Tony rips off his helmet and pushes the plastic mouthpiece between his teeth. He doesn't hear the noise his father makes, like a wounded animal, shock and horror and grief bowing Captain America's shoulders down.

Seth Rogers is twenty and in massive trouble. He doesn't think he's ever heard the words 'we'll talk about this when we get home' spoken with more ominous weight. Home, in this case, meaning Earth. Tony's gonna get it too - in the intervening fight he made it pretty clear that he'd known all along and had no plans to refuse Seth's... Exo's... aid. This battle goes down in history as one of Seth's most awe-inspiring achievements: in the end it was Seth, Tony, and Reed Richards working together at a frantic pace to overload and destroy Thanos' cosmic array. He worked with Reed Richards... Seth feels he's officially arrived.

It's really too bad his dad is going to kill him.

Except his father seems more sad than angry as they sit together in the waiting room of the medical wing at the Baxter Building. He leans his elbows on his knees, hands laced together, head bowed. Seth feels awkward. He doesn't know what to say. His Dad almost lost him today, but it doesn't seem fair to harp on that because Steve could easily have failed to come home from any one of his thousands of missions across so many years of service.

"Dad, I know what you're going to say."

"Do you."

"I have a pretty good idea. You've been saying it all along, right?" Seth sighs - his chest still feels a little tight but he's out of danger thanks to Tony's nick-of-time intervention. "I'm sorry I lied to you. But you never understood-"

"No," Steve interrupts, quiet and solemn. "I understand fine." Seth shuts his mouth and Steve chuckles bitterly, rubbing his gloved palms together. "How could I not understand? You're my son. I should have known. You'd never take no for an answer, you'd never accept doing any less than the heroes you grew up with. I wish I hadn't involved you. I wish I'd given you a different life."

"Why?" Seth demands. "So I could fail? So I could wonder for my whole life what I was missing? So I'd never know who I was, or what I could do? You always think this is about you," he vents, "this isn't about you, Dad! It's not about what you can do! It's about what I can do," he says passionately, willing his father to understand. "It's about who I am. I'm Seth Rogers and I can be a hero, not because it's in you, because it's in me. And I always knew it. You can't stop me," he reminds his father, voice cracking. "It's my life. I'm an adult now, and I'm going to fight. And if I die fighting, that's the choice I made and you can't say you wouldn't have made the same one because you already did. I've been prepared to lose you for twenty years," he says, trying not to sound bitter because that isn't what this is about. "Every time you went to fight you might not have come home. It's the risk we take. It comes with the territory. I understand. My eyes are open," he concludes, flexing his knee because wearing the specialized braces in his suit hurts after so many hours, the kind of pain that will have him curled fetal and crying later when it comes home to roost. "But I can do this. It's what I'm meant to do. And I love you, but I'll fight you for this if I have to."

Steve stares at him for a long moment and Seth wonders if he went too far, offered war when he hoped to win peace. But at length, his father smiles, runs a hand through his hair, gives a wry laugh. "Well. Guess it'd be pretty stupid for me to... butt heads with Captain America's kid. I'm getting pretty old," he observes, "and he can fly. That's one trick I never learned. You know, you were always so brilliant growing up. I figured in every single way except the physical you'd surpass me. But I didn't expect this. I'm not happy that you lied to me," he says, "but I understand why you did it. I wish... I wish I had known sooner," he confesses. "Not so I could stop you. But I missed all those chances over the last few years, with Exo on the news and in the papers, to say 'that's my son' and be proud of you."

Seth waits on tenterhooks. "So... we're okay?"

Steve offers him a world-weary smile of paternal acceptance. "You'll have to give me a lift sometimes. I get tired of riding everywhere on Tony's boot."

Seth laughs. "Yeah. But Tony wouldn't have it any other way."