Author's Note: Ok, so Endgame is truly an incredible movie and it really broke my heart. For some reason Mamma Mia really related to Stony's relationship for me so here's my take. In honor of canon, I've chosen to stick to many of canon story elements (though not 100% canon) in Endgame and relationship wise, which means including Pepper, Morgan and Peggy in the story and Tony and Steve's feelings about them and off course towards each other as well. Where possible I've made some changes to reflect Stony's relationship. I hope you enjoy this story as much as I did writing it.

I've been cheated by you since I don't know when

So I made up my mind, it must come to an end

Tony Stark felt everything. He knew he was on the brink of collapse but he had to stay awake. Him and Blue Meanie were saved. One last miracle. He thought he would never see them again. He already lost the kid. Tony wondered if Pepper was...or if he was…

A firm grip held him tight, supporting him. He turned to see Steve Rogers' blue eyes staring right back at his. He can't think about him now, not after what happened. He needs to find Pepper.

Tony sat in a wheelchair with a mobile IV drip. Steve asked him if the Purple Prune left him any clues as to where he might have gone. Tony Stark only felt rage. How dare Steve question him? He would've told them if the big Purple Nutsack said anything. They didn't even lose. They were flat out beaten.

"You know what I need?" Not you. Anything but you. I can't. I won't.

Rhodey tried to calm him down but enough was enough. "Why that otherwise, that what we needed was a suit of armor around the world! Remember that? Whether it impacted our precious freedoms or not, that's what we needed."

Steve merely said "Well, that didn't work out, did it?"

"I said we'd lose. You said, "We'll do that together too." Well, guess what, Cap? We lost, and you weren't there. But that's what we do, right? Our best work after the fact? We're the Avengers? We're the Avengers. Not the Prevengers, right?" Tony spat at Steve. Where were you when I needed you?

Steve stayed silent while Rhodey tried to hush Tony to sit back in his wheelchair. Tony had not even realized he had stood up. He barely registered the comment he made to Carol. Maybe she really is the new Captain the team needs. He ripped off his IV and staggered forward to Steve.

"Bunch of tired old wheels. I got nothing for you, Cap. I've got no coordinates, no clues, no strategies, no options. Zero, zip, nada. No trust, liar," he saw the hurt in Steve's eyes. Good.

He rips off his reactor and forces it in Steve's hand. Take my heart. It's already broken. I don't need it. But maybe, just maybe, this can save you. "Here, take this. You find him and you put that on. You hide…" His vision went black and collapsed.

Look at me now, will I ever learn?

I don't know how but I suddenly lose control

There's a fire within my soul

It's been five years since Tony came back from Titan. Five years since the Avengers took out Thanos. But they were too late. The stones were destroyed and everything stayed the same. They could not bring the others back. Since then, Tony had built a life with Pepper, and another miracle he had not expected, Morgan Stark. Tony was happy. He could not have asked for more though he wished he did not find his happiness on the world's loss.

He still remembered his first words to Steve.

"I couldn't stop him."

"Neither could I."

"I lost the kid."

God, he wished Peter was here to see this. He would have loved Morgan. She too would have adored him. Like a big brother. Working in the garage after school.

He saw Steve, Nat and was that Scott? pulled up at his front yard. Pretty soon, he knew why they were here. Time travel. Tony scoffs at the idea. Impossible. He immediately draws up all the possible scenarios that could go wrong with this plan.

But this is Steve asking. He had not met Steve since five years ago. He had something good going with Pepper and Morgan. They were the love of his life now. This Tony was an idiot. He had so many ups and downs, only nearing death that he realized he truly loved Pepper Potts. There was never any future with Steve. He made that very clear when he chose Bucky over him.

So he ended the discussion and sent them home.

Still he can't let go of the idea. He stared at the picture of him and the kid. Damn you Steve.

He had work to do.

Just one look and I can hear a bell ring

One more look and I forget everything, woah woah

Mamma mia, here I go again

My my, how can I resist you?

Mamma mia, does it show again

My my, just how much I've missed you?

Tony never expected for his invention to work. But it did. He could navigate through the Quantum Realm and time travel. Shit.

He tells Pepper about it. If only Pepper told him to stop and forget about this whole thing, he would. But Pepper isn't selfish, she knows how important this is. And he knows he is the team's best chance of success. Otherwise, if they don't take care of the Doidge proposition he may just end up looking after a bunch of Avenger babies. Literally.

Before leaving for base, he packed something he kept for a long time. The star spangled frisbee. He opened the wrapping to see it. The shield gleamed as if it was still brand new. He finds that he didn't harbour much resentment as he thought he would. Steve really hurt Tony bad the last time and he had called out Steve on it when they reunited. If they needed to succeed as a team, they both need to move past this. He still didn't really know what Steve Rogers meant to him now. They may not have worked out as a couple but seeing Steve again after all these years made Tony realize he needed his friend back in his life. He missed his banter, giddy optimism, leading the team alongside him, hell, even his prudishness to language. They were different people now than they were and he hoped that it was enough to move forward.

I've been angry and sad about things that you do

I can't count all the times that I've told you "we're through"

And when you go, when you slam the door

I think you know that you won't be away too long

You know that I'm not that strong

Just one look and I can hear a bell ring

One more look and I forget everything

Steve came out to think. Their experiment with time travel courtesy of Bruce and Scott had failed. Tony was right. I'm sorry I failed you Tony. So many words left unsaid. He still believe in the freedom to choose, not to follow any one organization's will. He did that once with SHIELD, and it almost cost everyone.

He should not have kept Bucky's secret from Tony. Bucky was his best friend, and after what they've been through, he wanted to keep it that way. He should have done the right thing but he was selfish and the price was him and Tony.

A familiar roar of the engine caught Steve's attention. Could it be? A sports car was heading towards the Base at top speed. He finds himself smiling already. There he is. Smug bastard already accurately guessing they could not fix the Doidge proposition. It's good to have you back.

The time heist, it is really happening. No do overs. The fight of our lives. Tony, Scott, Bruce and himself were travelling back to the Battle of New York, where all three Infinity Stones were in existence. Bruce goes off to collect the Time Stone. Steve himself has to retrieve the Mind Stone from then Loki's scepter. That left Tony and Scott in charge of the Space Stone Tesseract.

Steve was on his way getting into position to intercept the scepter when he heard Tony. "Ugh, Mr. Rogers, I almost forgot that that suit did nothing for your ass."

Did Tony Stark just checked out my ass? On open comms. This is so inappropriate. Well, he had gotten used to it when Tony used to flirt with him on comms during the mission. He used to blush at Tony's comments and his teammates would laugh. "Urghh. Get a room already you two." He couldn't suppress a smile forming on his face.

"No one asked you to look, Tony," he said smirking and shaking his head.

"I didn't," Tony insisted.

Scott decided to chime in. "I think you look great, Cap. As far as I'm concerned, that's America's ass."

"No do overs." They failed their shot at getting the Tesseract. Tony said he knew where they could get another shot at the stone and get more Pym Particles. Immediately, he understood what Tony meant. 1970. The old SHIELD base. Scott was not convinced it would work. If it failed, both of them would be stuck in that timeline forever.

"Do you trust me?" asked Tony. His eyes looked determined as if he wants to believe.

It was never a question for Steve. "I Do."

Steve felt nostalgic being back at the base after so long, in this timeline no less. Tony went to obtain the Tesseract in the vault while Steve was tasked with getting the Pym Particles. While Hank was distracted, he took enough for both of them to get home.

On the way out, SHIELD was already searching for them so he hid in an office. It had to be her office. Director Margaret Carter written on the door. His first love, Peggy. Then he saw her from the room. She still looked the same. The strongest person he's ever known. A lady in a world of men in that era and she made her way up to build SHIELD with Howard. His heart ached when he thought of what he could've had with Peggy. God, I miss her so much. I'm sorry that I still owe you that dance Peggy.

He thought about Tony and his life with Pepper and Morgan. Despite what happened between them, Steve had always wished the best for Tony and he was glad that he finally found happiness with them. Peggy was someone Steve treasured and a missed opportunity but with Tony he knew he found happiness. He just had to go mess it all up. A pain still permanently seared in his heart when he heard Tony's words "So Was I." "Liar."

Later on, he saw Tony talking and hugging Howard. Steve felt joy and relief that Tony got that rare moment in the thick of things. It was unfair that his family was taken away from him.

Despite all odds, they made it back with the Tesseract. After experiencing what they've been through, Steve vowed that he'd do whatever it takes to protect Tony so that he could have his happy ending.

Yes, I've been brokenhearted

Blue since the day we parted

Why, why did I ever let you go?

Mamma mia, now I really know

My my, I could never let you go

Steve could not fulfill the vow he took on to protect Tony. He tried. It took everything in him to charge towards Thanos. To get Tony out of the way. He could not make it. Tony took the stones. His last words "I am Iron Man" and snapped all of Thanos' forces into dust. An eye for an eye. He saw Peter go up to a dying Tony who couldn't say anything. It shattered Steve's last resolve. Pepper touched her forehand tenderly towards Tony. "Tony. Look at me. We're going to be okay. You can rest now."

He saw the life fade from Tony's eyes. I failed you Tony. I failed you in every way.

Bucky found him hiding in an empty room. It was the day of Tony's funeral. Hot tears streamed down Steve's face as his best friend sat beside him.

"They're about to start," said Bucky.

"I...I...can't. I failed him Bucky. I failed the man I love…"

"You did not. You tried. Everyone did. We won and the universe is saved...just that there's a cost to pay"

"Yea and I was all about 'We don't trade lives'. Look at Nat, and Tony. I was supposed to protect him, I couldn't give him the happiness he deserved but at least he would be alive, living with Pepper, seeing Morgan grow up. What is even the point of wielding Mjolnir? Wasn't I worthy enough to save everyone, to take on the burden, so that Tony wouldn't have to?"

"You can't save everyone. Thor couldn't and he's a god. Thanos pretty much thought he was a god and he wasn't omnipotent. Some day, Steve, you have to find it in yourself to forgive yourself."

"I can't right now."

"I know," said Bucky patting Steve's shoulder. "But maybe you could try to honor Tony's request of you, the one you told me about? To live your life."

Steve was ready with the Infinity Stones placed in the briefcase and holding onto Mjolnir. He told Bucky of his crazy plan to be with the love of life. He thought it about for a long time before deciding to go for it. He expected Bucky to talk him out of it but Bucky didn't. He wished him the best in life and they will see each other again soon.

"Don't do anything stupid until I get back," said Steve to Bucky smiling.

Bucky grinned back. "How can I? You're taking all the stupid with you."

They hugged one another. It'll be a long time before Steve sees his best friend again.

"I'm going to miss you, Buddy," said Bucky

"It's going to be okay, Buck," he said as he stepped onto the platform.

He chose to drop off the Tesseract last. His journey in returning the stones have been an interesting one, not to mention somewhat disturbing but that is a story for another day. Right now, he was at Peggy's door step. Live your Life. He knocked.

Peggy opened the door and stared at him. It was not often that Peggy Carter was speechless. "It's me," Steve said. She teared up and hugged him tightly.

Steve could spend hours talking to Peggy. He wanted to know what happened in her life and she wanted him to tell her all of about his. He could stay here. Live his life with Peggy like he had always wanted. As he told Peggy about his post-frozen adventures, he realized that a lot of the moments he remembered and treasured mostly revolved around him.

It appeared that Peggy too had found love in her life. His name was Daniel Sousa. Steve remembered him. He had saved Sousa before on one of his missions. He was a good man.

"I'm sorry Steve. I know why you're here and in another lifetime if you didn't end up in the water, we could have been together. I love you Steve Rogers. I always have. But now I'm in love with Daniel," said Peggy tearfully.

"I know Peggy. You're lucky to find Daniel. A love like that does not come by often," said Steve smiling. "Don't worry about me. I'll be okay. I'm going to live my life too and we'll see each other some day."

He stood up, went to turn on the music record, and extended his hand to Peggy. "But for now, Peggy, would you care to have this dance with me?"

Peggy blinked her tears away. "Yes, Steve. I would love to."

They held each other in their arms, swaying to the rhythm. Steve was still not a good dancer but it was the best dance he ever had.

Live your Life. Steve Rogers traveled through the branches of alternate realities. He was careful not to disturb the other timelines, only observing. He was not sure on what he was doing. In many realities, Tony had a Steve Rogers in existence. In some, Tony was married to Pepper. In others, Tony was dating and eventually married Steve. There was even a few where Tony was with neither and ended up dating Stephen Strange. Steve did not wanted to jump into any of those realities and ruin their happiness.

There was only once where Steve intervened where an alien assassin was aiming at Tony from behind. Tony did not see it and was helmetless. This reality did not have a Steve Rogers. Tony was the only leader of the Avengers.

Steve rushed out and pushed away Tony in time for the shot to miss. Knowing failure, the alien assassin sent a group of extraterrestrial looking mercenaries after Tony. Tony suiting up his Iron Man armor and Steve in combat stance quickly defended one another. "Who are you?" asked Tony incredulously.

"I'm Steve Rogers," said Steve simply while fighting off the onslaught.

"Well, thank you, Steve Rogers. For saving me today. Hey, you wanna grab a meal with me? As a thank you, I mean."

"Sure. But after we take down these alien goons first."

"Righttt. How does Shawarma sound? Tonight, I know a place. I actually don't know what it is but I wanna try it."

Steve could not hide his grin. "It would be my pleasure."

Since then, Steve officially joined the Avengers as Captain America. He quickly rose up the ranks and eventually co-lead the Avengers alongside Tony. He even received a new Captain America shield built by Tony from Wakandan vibranium courtesy of T'Challa. From a personal aspect, Steve spent some of his best days with Tony. He was mindful to be always honest with Tony, no matter what. In turn, while certain turn of events had taken a toll on their relationship, he always had Tony's trust.

Life with Tony was always going to be a roller coaster but they eventually got married in front of their family, the Avengers and pretty much adopted Peter as their son. As the years went, they both grew older and handed the reins to the next generation of Avengers.

They retired in a cottage in the woods, away from the public eye, where Tony still spent his days in the workshop working the latest invention with Steve helping him out. When he's not in the workshop, Tony would help Steve cook and clean. After that, they would sit by the couch leaning into each other, watching the telly. Other times, Steve and Tony took turns to surprise one another, whether is an outing, a dance or coming home to giant teddy bear, they made it work. Steve was no longer the man out of time. He had lived a full and happy life with Tony. Once Tony had eventually passed, he knew it was time to return back to his own timeline.

Steve sat on the old bench looking towards the lake. He heard Sam walk towards him.

"Cap?"

"Hi Sam."

Sam stood and observed while Bucky had a knowing smile. "Sooo...did something go wrong? Or did something go right?"

"Well, after I put the stones back, I thought, maybe I'll try some of that life Tony was telling me to get."

"How did that work out for you?"

"It was beautiful."

"I'm happy for you. Truly."

"Thank you."

"Only thing bumming me out is the fact I have to live in a world without Captain America."

"Oh, that reminds me…" said Steve as he took out his shield from the wrapper and handed it to Sam. "Try it on."

Sam looked stunned as he turned to Bucky who gave him a nod of approval. It was never Bucky's intention to take over for Steve. Bucky had lived his life in war and chaos. Now, he wants to live out the rest of his life in peace. The White Wolf will come when called but it was never the life Bucky had wanted.

The shield in Sam's hand looked so natural. "How does it feel?" Steve asked.

"Like it's someone else's," Sam answered.

"It isn't."

"Thank you. I'll do my best."

"That's why it's yours," said Steve smiling as he shook Sam's hand.

Sam eyed the wedding band on Steve's finger. "You want to tell me about her?"

"No. Not really," said Steve cryptically.

Sam paused and asked again "You want to tell me about him?"

Steve broke into a knowing smile "No. I don't think I will."