Work Text:
You were supposed to swap bodies with your soulmate for one day every ten years. The countdown started when the oldest soulmate was born— usually, soulmates didn’t have an age gap more than a couple of years.
Tony had waited patiently for the day to come where he would wake up in another person’s body, walk in their shoes and live their life as many times as he could. His tenth birthday had been a huge disappointment, which was probably why he started drinking at such a young age. What good was the heir to Stark Industries if he didn’t have a soulmate?
Then, Tony went to MIT and met James Rhodes, who also didn’t have a soulmate, and had no desire for one. That was the main thing that divided the two of them— Tony wanted a soulmate, he didn’t care about gender or looks or any of that, he just desperately craved someone to understand him, while Rhodey was the complete opposite.
“It’s not so much that I hate the idea of soulmates,” Rhodey explained one night, both of them pleasantly buzzed on alcohol in their sophomore year of college. “I just don’t want one. There are things I want to do in my life— join the Air Force, serve my country, make a change, yadda yadda. But I feel like if I could do them, I would be happy with my life and feel fulfilled without a soulmate, y’know?”
Tony didn’t know, but he pretended like he did anyway.
Rhodey was the reason Tony stopped drinking. Maybe he wasn’t as broken as Howard always tried to tell him he was— he was just slightly different from the norm.
He still made his rounds, though, and dated occasionally. His longest-standing relationship was with the lovely Pepper Potts, but they had broken up on amicable terms after a couple months, agreeing they were better off as friends.
They still argued like an old married couple, especially when Tony locked himself up in the workshop and hyper fixated on a project so much he didn’t eat or sleep for a few days.
But it was okay. He’d lived over four decades without once swapping bodies with someone, and he was fine with it.
Sometimes, he remembered what had happened two years ago, and how badly both he and Steve had screwed up— God, Siberia— and he wished he had someone who would understand. That only happened when he was really low, though, when he would stare at Steve’s drawings that he couldn’t bear to take down and pull out the shitty not-apology letter.
Tony Stark knew he didn’t deserve a soulmate.
And yet, fate was a fickle little bitch.
_________________
Steve had always assumed that his soulmate had been the one thing that Erskine’s serum hadn’t been able to fix. It was okay, he’d made his peace with it— his soulmate was probably ancient, in any case, or taking an eternal dirt nap.
Steve had believed that the gorgeous Margaret Carter may have been the one, but she had revealed that she had a soulmate: a woman named Angie. Steve had seen the stars in Peggy’s eyes back in the forties when she had talked about this woman, and accepted the fact that he was just destined to be mateless.
A small price to pay, for what he has accomplished.
(Steve vowed he would take the secret of Peggy’s soulmate to his grave, knowing it was the only way he could protect her. He was glad it worked out for them despite the bigotry and hate they’d had to face along the way.)
It was okay. Steve didn’t want a soulmate, anyway (he yearned for one). If they were an acceptable age, he would probably outlive them due to the serum, assuming he didn’t do something stupid and die in the middle of a battle where they could do nothing to help.
It was okay, seeing Sam waking up one morning, looking sorely confused, before turning to Steve and softly saying, “You’re… You’re Captain America?” in a way that could only mean it was Sam’s Swap Day.
It was okay, hearing how Clint got to spend all the time he’d like with his kids and his soulmate now that he was on house arrest.
It was okay, because Steve had Nat, and Nat’s connection to her soulmate, whoever they may be, had been severed in the Red Room. Steve had Bucky, too, whose connection was also cut during his years with Hydra.
It was not okay when he woke up one morning, approximately half a head shorter and on the couch in Tony Stark’s personal workshop.
_________________
Tony woke up with a groan, feeling… well, better than he had in years. His bones didn’t ache from sleeping on the couch, he felt like he could function somewhat without coffee, and oh, hello, he was around half a foot taller and trapped in the body of a super-soldier.
Upon coming to this realization, he stumbled upright, crashing into the wall as he made his way towards what he assumed was the bathroom. He flicked on the light, and fuck, yep, there was Steve Rogers’ chiseled face staring back at him.
The good Captain was also rocking a beard now, which Tony didn’t know how to feel about.
A light tap on the doorway outside started Tony, and he peered out of the bathroom to see Natasha staring at him skeptically, yet looking faintly amused. Her hair was straight and cropped at her chin, but the strangest thing about it was that she was platinum blonde. Tony thought he would die before he would see Nat get a gray hair, let alone change her hair color, but apparently, that was not the case.
“You okay there, Stevie?” she asked, smirking. “You were making quite the racket there for a moment.”
Tony’s fight-flight-or-freeze instinct kicked in, and he tensed, trying to figure out what to say. Had it been Steve’s buddy Sam, or even Wanda, Tony wouldn’t have been able to tell the truth. But this was different.
This was Nat.
Besides, she was going to find out soon, anyway.
“Nat,” he said quietly, and his voice wasn’t his voice hisvoicewasn’thisvoice, and Natasha’s expression immediately hardened into suspicion. “I’m going to tell you something, but you have to promise you’ll use your ultra secret Russian spy superpowers for the good of all humanity and never tell a soul.”
“Steve,” Nat said slowly, “why are you being a bigger drama queen than To…”
She trailed off as Tony scrunched up his face— it probably looked extremely wrong on Captain Perfect’s features, but it was all Nat needed to know. The suspicion drained away and was instead replaced by… horror?
“Tony?”
“In the flesh! Or, no, maybe not, since I’m technically in Steve’s body. Look, let’s just say I’m fifteen percent confused and eighty-five percent still extremely guilty about everything that happened two years ago, so can we please just forget I’m here and get today over with?”
Nat huffed out a sigh, though it sounded fond. She crossed the room and hooked one hand around the back of his neck, bringing his forehead down to rest on her shoulder.
“I missed you, Shellhead,” she murmured. “We’ll figure this out.”
“Thanks,” Tony said quietly. “And for what it’s worth, I missed you too.”
_________________
Steve groaned as he sat up. His chest ached, and it hurt to breathe in a way he hadn’t experienced since before Project Rebirth. The beginnings of a headache were pounding away in his temples, and his bones ached in an unfamiliar way.
Steve scrubbed a hand down his face, slightly surprised to feel stubble in concentrated areas rather than the full beard he had decided to grow whilst going undercover as Nomad. He glanced around, gathering his bearings— Tony’s arm-robot, who Steve had heard Tony call “Dummy,” was whirring away quietly in the corner of the workshop. Multiple projects that looked deadly on various levels were scattered across the tabletops, a holographic schematic for… something still running.
“FRIDAY?” Steve asked quietly, jumping slightly at hearing Tony’s voice instead of his own.
“It is currently seven thirty-two in the morning, sir,” the AI replied pleasantly, her tone gentle. “Temperature outside is seventy-two degrees Fahrenheit, partly cloudy, and low humidity. You have three unread emails from Miss Potts and two unread messages from Colonel Rhodes.”
“Uh, thanks,” he responded, awkwardly pushing himself off the couch and to his feet. Tony’s clothes were oversized, rumpled, and smeared with grease— nothing out of the usual.
Okay. This was fine. He could do this.
Tony is your soulmate, Steve realized.
Yeah, no. He couldn’t do this.
_________________
“I think it would be better to tell them,” Nat admitted as Tony nursed a cup of coffee. He now understood why Steve had such a big sweet tooth— apparently, Project Rebirth had made Steve’s tongue about a thousand percent more sensitive to everything he put in his mouth, so there were no more half-drunk cups of room temperature black coffee for Tony. At least, not for today.
“Yeah, maybe,” Tony agreed. “I should probably call him— or me— or whatever first. He has a phone, right?”
Nat raised an eyebrow, stirring her tea with a spoon and looking thoroughly amused. “Bedside table. Top drawer, I believe. Let me know if anything explodes.”
“Will do,” Tony replied, pushing himself up from his chair and giving her a two-fingered salute.
“Oh, and Tony?” she added, just as he was crossing the threshold into Steve’s room. Tony turned on his heel to face Nat, whose expression had gone as hard and cold as steel. “Please be patient. He still hates himself for everything that happened.”
With that, she elegantly stood up and stalked off, leaving Tony to watch after her, confused. Steve didn’t tell her about Siberia, did she? he wondered.
The phone, shockingly, is a StarkPhone— not the latest model, but also not old enough to make Tony cringe at the sight of it. There’s only one number in it, so after taking a deep breath to calm himself down, he presses Call.
It only rang twice. Tony hoped it was because Steve was thinking the same thing as him.
“Hello?” Steve asked, but it was Tony’s voice saying it, and oh God that was weird.
“Whoa,” Tony said before he could help himself. “It is really weird to hear my own voice talking. It’s probably weird for you, too. This is crazy.”
“Sta— Tony.” Steve didn’t sound amused. “What is… does this mean…?”
“It means,” Tony said with a long-suffering sigh, “that we’re soulmates, Cap.”
_________________
When Pepper came in to check up on Steve, he told her the truth.
He thought he saw a tear in the corner of her eye as she nodded and told him where Tony kept the phone Steve had given him.
He wasn’t sure which surprised him more— her calm, steely reaction, or the fact that Tony had kept Steve’s drawings in his office.
_________________
Bucky scowled at Tony when he told them.
Wanda gasped.
Sam muttered something that sounded like, “I fucking called it,” under his breath.
Nat just offered him an encouraging smile as Tony choked on apologies.
_________________
One day.
That’s all it took for history to change.
_________________
The next day, when everything was back to normal- when Bruce Banner fell from the sky and crashed into where Dr. Stephen Strange resided, and shortly after, a donut-shaped spaceship landed in New York (honestly, Tony had no idea how that thing traveled through space. It was seven different levels of Engineering Pain just looking at it)- Tony didn’t hesitate.
He called Steve beforehand.
_________________
Steve received the call in Wakanda. There wasn’t anything he could do about the spaceship in New York, but when Thanos and his army reached them, they had more time to prepare.
_________________
They still lost.
_________________
Steve lost Bucky, and Sam, and Wanda.
When it finally hit him, what had happened, he clung to Natasha and sobbed.
His soul bond was numb.
_________________
Tony’s hand was coated in Peter’s ashes, and Nebula was shaking like a leaf in the wind by his side, but all he wanted was the stupid phone to work.
Cell service should be a thing in space.
Tony should have made that.
Cell service in space— so he could call Steve. Tony just needed to know that he was okay. He couldn’t tell whether he was coping with grief or if the emptiness in his chest was a broken soul bond, and the anticipation was slowly killing him.
Too bad Tony could barely get the stupid fucking spaceship up and running. Tony blamed Peter fucking Quill for all of this— couldn’t he have waited five more seconds to punch Thanos in the face?
Now the kid he thought of as practically his son was dead, he was dying of a stab wound in his chest, and why did Strange have to give Thanos the time stone?
Tony had been so willing to die. So willing. He would have ensured that Peter could have had a solid job at Stark Industries, and he had plans to let Steve and everyone who sided with him for the Accords be granted full amnesty, and—
And, well, Steve had only known he was Tony’s soulmate for a day. He deserved so much better than Tony, anyway.
_________________
Seventeen days after the Blip, a woman named Carol Danvers showed up, briefly pausing the agony and turmoil in Steve’s mind to give him a glimpse of hope.
Steve took an instant liking to her— she was calm and cool and had a sense of humor Tony would adore. She was also a former pilot for the United States Air Force, a captain like him, and was thought to have been killed in action back in 1989 before magically reappearing in 1995. Apparently, she knew how Nick Fury had gotten his eyepatch, but she refused to share, grinning sadly when she denied every time somebody asked.
They had a lot in common, except Steve couldn’t breathe in space. Or glow.
_________________
When Tony finally landed back on Earth, he could only barely register Steve’s face— now clean-shaven— and his perfectly sculpted body hurtling towards him before he was enveloped in a hug. Steve helped him down the stairs, and it was all Tony could do to stop himself from burying his face in the crook of Steve’s neck and staying there until they both withered away and the earth reclaimed their bodies.
“I lost the kid,” Tony croaked, watching the flash of hurt in Steve’s blue eyes.
“Tony,” Steve said, just as quietly, just as softly, “we lost.”
_________________
Tony was yelling, and Steve couldn’t hear a single word he said over the ringing in his own ears. It felt like everything was underwater— he knew this feeling, knew there was nothing he could do to stop it, but the tendrils of panic wound their way around his ribs regardless, tightening across his lungs, cutting off his airways.
Tony pressed himself against Steve, chest-to-chest, his brown eyes filled with fury and hurt behind his glasses. “No coordinates, no plan, zip, nada, nothing. No trust.
“Liar.”
The word was spat, and all Steve could do was blink the tears from his eyes as Tony tore the arc reactor from his chest and slapped it into his hand.
You broke my heart once, go ahead and break it again.
Steve caught Tony when he collapsed.
_________________
Steve had forced Tony to stay behind as they all went to fight Thanos and undo the Blip.
Tony hated every second of waiting for them to return— hated that he was worried more about Steve than the others even more.
_________________
It was too late.
Thanos had won.
Steve returned with empty hands.
Tony didn’t yell, but the look of disappointment and shattered hope on his face hurt more than any spiteful words.
_________________
Despite Tony’s best efforts to drive him away, Steve stayed.
Little by little, they began to heal.
One day of switching bodies did not make up two years of stewing hurt and heartbreak.
_________________
Five years passed.
Natasha became in charge of helping Earth recover.
Carol and Rocket went off across the galaxy, checking back into Earth every now and then for a drink and to catch up.
Rhodey worked to try to hunt down Clint, who had gone rogue since his family had been Snapped away.
Thor relocated the surviving Asgardians— unfortunately, there weren’t many— to a small town in Norway, so they could have a little taste of home. Bruce, as his soulmate, went with him, and somehow accepted the Hulk into his body, so the “other guy” was no longer a problem.
Tony practically adopted Nebula— a quiet, cyborg alien who really just needed a hug— to help him and Stark Industries focus more on clean energy and medical technology than ever. The world needed any positives it could hold onto.
And Steve?
Well, he took up Sam’s place as a community therapist. He was doing okay, helping people move forward.
And every night, he went home to the cabin on the lake, kissed Tony on the cheek, and made dinner for them and Nebula.
_________________
It took time.
Tony had to accept the fact that Captain America— Steve Rogers— the man who had been his idol and his enemy his entire life, was his soulmate. He had to accept that they were both in the wrong for the Sokovia Accords, and they had both broken something in each other that could never truly be fixed.
It took a lot of time, a lot of nightmares, a lot of indirectly seeking each other out, before he was truly comfortable with himself and whatever the fuck his life was now.
But now, five years since the Blip, he could watch Steve hum along to whatever classic rock song was playing as he cooked dinner, the picture of Peter at the “internship” grinning down at them as Nebula smiled softly and danced around in the kitchen.
He could watch them and know that this was what home felt like.
_________________
They slept together for the first time two years after the Blip— two years after they swapped bodies and discovered that they were soulmates.
The bond flared every time they kissed. It was slow, and sweet, and more like making love than an ugly fuck. Somewhere through the foggy, pleasured haze that was his brain, Steve knew that being burned alive shouldn’t feel this good.
As Tony leaned up to lock lips with Steve as he continued his pace, staying slow even when Tony begged for more, Steve had no doubts that this was the best night of his life.
_________________
Tony was planning on proposing when Scott Lang showed up at the door of the Avengers Complex.
Sure, he gave them hope, but he gave Tony a shit ton of problems.
He’d already made the rings— painstakingly scraped off shavings of vibranium from Steve’s shield and broke off a piece of the Mark VII, melting the two metals together to create two bands of swirling silver and gold.
But, well, he could whip up a way to safely time travel in a night instead of staring at the little velvet box like he usually did. While making the final adjustments on the nanosuits, though, he built a small pocket to store the box in.
Hey, it would be kind of fitting, if he proposed on the battlefield.
_________________
Steve found himself back in 2012, around a year after he had been freed from the ice. Bruce had run off to the New York Sanctum to get the Time Stone from Stephen Strange (and, well, if push came to shove, he was the best bet for muscle) while Scott, Tony, and Steve were to go back to the Avengers Tower.
“Ugh, Mr. Rogers, I almost forgot,” Tony crooned into his earpiece, practically taunting. “That suit did nothing for your ass.”
Steve felt the tips of his ears turn red as he resisted the urge to glare at where Tony and Scott Lang were hiding. “Nobody asked you to look, Tony.” Hopefully, Tony wouldn’t be able to pick up the smile in his voice.
He made his way into the elevator, conned the Hydra shits out of Loki’s scepter, all while stifling a smug smirk, and made his way out.
“Hey, Tony, I’ve got the—” he froze when he saw the 2012 version of him, still wearing the stupid cowl and suit, approach, scowling. “Hold on.”
“Okay,” Tony replied, snickering. Only he would think giving himself a heart attack is funny, Steve thought, exasperated.
“You shittin’ me?” Steve asked his past self, raising an unimpressed eyebrow.
“I have eyes on Loki,” 2012-him reported, nervously touching his own earpiece, still reveling in the unfamiliarity of it all. “He has the scepter.”
Steve dropped the case and nudged it out of the way with his toe. 2012-him followed the move with his eyes. “I’m not Loki,” he told himself, but would 2012-him agree?
No, of course he wouldn’t.
2012-him lunged, bringing his shield up over his head, and Steve maneuvered his arm in just enough time to block the blow with his own shield. The vibranium clashed with an ear-splitting shriek, causing sparks to shower down upon them.
The thing about fighting yourself? You knew all your own weaknesses.
And the other version of yourself knew them, too.
Somehow, Steve managed to lose his shield and 2012-him had him in a headlock, the inside of his elbow pressing against Steve’s Adam’s apple, choking him. Steve struggled fruitlessly for a few moments, then thought up a better strategy. He was the Star-Spangled Man with a Plan, after all.
“Tony… is… your soulmate,” Steve wheezed. He felt 2012-him’s grip slacken, and for good measure, he added, “and Bucky killed his parents,” before whirling around and knocking 2012-him out cold.
With a sore throat and bruises that would fade within an hour blossoming on his skin, Steve doubled back to retrieve his shield and Loki’s scepter. He glanced once more back at 2012-him, his attention immediately drawn to… well…
“You’re right,” Steve said into his comm. “That is America’s ass.”
“Love the realization, but can you head down to the outside?” Tony said, sounding sullen. “We’ve got ourselves in a bit of a situation, here.”
_________________
Tony had panicked.
He panicked when the lady in the elevator stared at Steve a bit too long, he panicked when he saw his father, he panicked when Howard lied about loving him, and he panicked when Steve told him that he’d seen Peggy.
But they were here now, back at the Avengers complex in upstate New York in October of 2023, and they had the Tesseract.
Once this is over, Tony promised himself, tangling his fingers together with Steve’s, I’ll propose.
_________________
Nat was gone.
Steve buried his face into Tony’s shoulder and sobbed.
_________________
Tony realized that Nebula was not his Nebula a moment too late.
By that point, Thanos of 2014 already knew what was going on.
Tony felt awful for not having recognized his own daughter sooner.
_________________
Bucky was back.
Bucky, and Sam, and T’challa, and Peter Parker and Hope van Dyne and all the others that had been turned to dust five years ago with the snap of Thanos’ fingers.
They fought beautifully. Valiantly.
Steve finally lifted Mjölnir— he knew he could, back in 2015, but the team was still fresh and tender, and he hadn’t wanted to cause any dispute over being the only one worthy enough to wield the hammer besides Thor himself.
Oh, if 2015-Steve could see himself now.
_________________
Stephen Strange lifted one shaky finger.
Tony’s heart sank into his stomach, and his hand automatically shot to where the velvet-lain box was kept safe within his armor.
Sorry, sweetheart, he thought. Maybe I won’t get to propose, after all.
_________________
Together.
The words Steve had said in the past didn’t echo in his ears— they roared.
He recalled something Rocket the not-raccoon said once, about how he and the other Guardians of the Galaxy had shared the might of the Power Stone.
Steve knew the look in his soulmate’s eyes, he knew Tony was about to do something crazy.
_________________
It was like some cheesy Justice League movie.
Everyone held hands, starting with Tony, then Steve, then Thor and Clint and Carol and Peter Quill and Shuri—
Thanos and his army disappeared.
Tony fainted into Steve’s arms.
_________________
Steve took a deep breath, stepping up to the platform with the case of Infinity Stones.
He knew what he had to do.
_________________
Tony’s first reaction, when Steve returned, was to break down sobbing.
The second was to lunge at Natasha and hug her as tightly as fucking possible.
Tony proposed to Steve in front of Bucky, Sam, Natasha, Bruce, and the time-travel platform he’d whipped up on his sixty-second hour without sleep and twelfth cup of coffee.
He wouldn’t have it any other way.
_________________
They had their wedding in the spring.
Steve chose Bucky as his best man and Natasha as his maid of honor, while Tony picked Rhodey and Pepper. Nebula was the flower girl, and Peter Parker was the ring bearer.
Both Steve and Tony cried while saying their vows. When the officiator declared them husbands, Steve twirled Tony into a dip and kissed him with a little too much tongue to be considered socially acceptable.
It was perfect.
_________________
Sometimes, Tony still liked to wonder what would have happened if they hadn’t swapped bodies the day before the Infinity War began, or if soulmates didn’t exist in the first place.
It made him glad that, for whatever reason, the universe had chosen him to live this life instead.
Because honestly, Tony never thought he’d get the happy ending he received.