This doesn't follow Endgame, but there are a few minor things taken from it so fair warning.
"Hey, have you guys seen Spider-kid anywhere?" Tony asked as he and Pepper walked up behind Sam, Barnes, and Natasha, the latter of whom smirked and pointed forwards.
Tony turned, only to feel his jaw drop at the sight before him.
The kid he'd just been asking after was currently lying back on a weight bench holding the bar aloft. This wouldn't be too alarming, except the bar Peter was holding was not only playing perch to Shuri, Loki, and Lila (the first two girls sitting on either side with the last balancing on the center), but was also being loaded down by weights Tony knew were specifically designed for the likes of Hulk, Thor, and Steve because he was the one who designed them.
Steve and an armored Rhodey were the ones doing the loading while Thor stood by Peter's head like an over-enthusiastic spotter. Behind them, Harley appeared to be recording the whole thing from atop a beanbag chair while Strange meditated midair next to him. Cassie was leaning against Dog on Harley's other side, eating popcorn and tossing pieces of jerky to the giant ant while Groot laid next to her playing a video game.
"What is going on here?"
Peter lifted his head just long enough to give the man a smile before refocusing on his task. "Hey Mr. Stark, can't talk now."
Tony turned to Natasha for an explanation, but Strange spoke up before he could.
"They are testing to see how much weight he can handle." He opened an eye. "For the record, I don't approve. I am only here in case medical aid is needed." He closed his eye.
"Also for the record, we just got here," Sam added, giving Tony a nervous look and gesturing towards himself, Barnes, and Natasha.
"And what's your excuse, Capsicle, Point Break, Rhodey?"
Steve shrugged and carefully added another weight to the bar in time with Rhodey. "The kids were going to do it either way. I figured it was better they had someone to supervise. Besides, it is good to know your limits."
Barnes snorted.
"I was also made aware that it is better to have someone to help manage the weight, which none of the young ones can do," Thor added.
Loki sent him a look. "I could handle it."
Thor gave her a smile. "I'm sorry, sister. You just look so small in your new form that I misspoke."
The reborn goddess scowled then suddenly transformed into a man taller than Thor and as hulking as, well, the Hulk. "If I wished to appear a brute like you, I would," he said in a gruff voice.
"Woah, Loki!" Peter yelped as the bar tilted with the unexpected extra weight and Lila stumbled, just managing to catch herself before she fell.
Shuri, meanwhile, looked unaffected, if a bit amused.
"Apologies," Loki said, returning to normal, though the teen remained male.
Unfortunately, this merely had the opposite effect as Peter's compensation for Loki's added weight that no longer existed sent the bar careening the other way. Lila did fall off this time, thankfully into Thor's waiting arms, while Shuri slid off the bar and onto her feet.
Loki was tossed onto Peter, who huffed at the impact and barely managed to keep ahold of the bar.
"Alright, I think that's enough for today," Tony snapped and Steve and Rhodey immediately moved to take the bar from Peter.
The kid grudgingly handed it over to the "Boo!"s of Harley and Cassie and the jeering "I am Groot!"s of said talking plant.
Loki pulled himself off the older boy, dusting himself off and giving Thor an annoyed look. "This is all your fault."
Peter jabbed him in the side with his toes, saying breathlessly, "You're the one who shapeshifted while sitting on the bar!" He then rolled off the bar before Loki could retaliate, coming to stand next to Shuri.
"Alright new rule, Young Avengers, no playing around with the heavy weights," Tony said, crossing his arms.
Loki, as per usual for learning about any new rules being placed against him, looked affronted while Peter just pouted at his mentor. The three off to the side looked unaffected, Groot already having returned to his game and Cassie and Harley shrugging it off.
Lila, who was now sitting on Thor's shoulder, crossed her arms back at him. "How are we supposed to test Buggy's strength if we can't use the good weights?"
"Buggy?" Peter muttered and Harley snorted.
"Now you know why I turned down Ant-Girl," Cassie chuckled.
Loki tapped his chin, "He could lift up a car, then we could just put heavier and heavier things in or on it until either the car gives in or he does."
"No. No, no, no. No more ideas from you, Orpheus," Tony cut in. "I will come up with something. Something that won't end in him being squashed by a car."
"I would have spotted for him," Loki tutted with an eye roll.
"Come now, the young ones are just having fun," Thor said, coming over to slap Peter's back. Lila, still on his shoulder, laughed as the boy stumbled. "And your son has proved he has the strength to stand with the mightiest of heroes. You should be proud."
Tony opened his mouth to say he would be prouder if the kid would stop pulling stupid stunts before Thor's words truly caught up with him. "My what now?"
"Your son," Thor said, frowning. "Peter."
"He's not my… You thought the kid was… I don't have a son!" Tony sputtered and darn it he could hear Pepper giggling behind him.
"He's not yours?" Thor said deflating.
"No! Why would you think that?"
"Well, you know, the… technology…"
"Wait, Spidey's not yours? Like seriously?" Sam asked and Tony turned to see him and Barnes giving him unconvinced looks.
"He's seventeen! Pep and I've only been married for -"
"All due respect," Strange cut in, dropping to the ground. "But I doubt anyone thought he was Mrs. Potts'. Just yours."
"And what's that supposed to mean?" Tony asked, narrowing his eyes at the sorcerer.
"Considering your past, it's not inconceivable that you'd father an illegitimate child or two."
"Despite what you and many others might think of my past, I was very careful during my past… interactions," Tony trailed off, very aware of his wife standing at his back. "I have no illegitimate children."
"No matter how many women have tried to say otherwise. For the record, I had paternity tests done for both Harley and Peter ages ago."
Tony spun around towards her and Pepper rolled her eyes.
"Only so that we'd have proof in case such rumors started going around the news feeds when the two became more public. In case your forgetting, I was the one who always had to escort your interactions out. I'm perfectly aware you've covered your bases."
"So?" Barnes asked. "What were the results?"
Pepper chuckled as Tony turned to scowl at him. "They were both negative."
Tony threw his hands up. "Alright, raise your hand if you thought Underoos was my kid!"
After Steve confirmed that Underoos referred to Peter, everyone in the room raised their hands save Loki, Natasha, Harley, and Pepper.
"Rhodey!" Tony shouted at his best friend, who shrugged as much as he could in the suit.
"I thought you were just trying to keep it on the down low."
Something registered in his mind before Tony could continue yelling. Slowly he turned to Peter, who dropped his arm with a blush.
"Awkward!" Harley called cheerfully.
Peter shot him a look. "Oh like you never wondered why Tony's always giving us attention out of literally anyone else in the world."
Harley shrugged. "Nah. Though I think my mom's still half-convinced she had a drunken fling with him and just can't remember. Kind of wish she had, though. He's already a better dad to us than my dad was to me and he doesn't even dad us."
"He totally dad's you," Cassie snorts. "He's seriously got that whole dad-aura whenever he's around you two and Morgan that he doesn't have any other time."
"I am Groot," Groot said, shaking his head. "I am Groot."
"He said you have the appearance of sharing roots," Loki translated. "Also, you talk the same. His words, not mine."
Lila nodded. "I would have thought he was your dad even if dad hadn't told me you guys were father and sons."
"Clint told you they were related?" Pepper asked and Lila nodded.
"He knows they're not," Natasha said, shaking her head. "He was messing with you kids."
Lila laughed. "Yeah, I figured, Auntie Nat."
"Wait, when did I get dragged into this?" Harley asked, sitting up. "People think I'm his kid too?"
"Obviously," Shuri said.
"Hey, I think we broke Stark," Loki said, smirking at a frozen Tony.
The genius was still gaping at Peter.
"Tony?" Pepper whispered, setting her hand on his shoulder. She turned to the others. "Alright, I think that's enough excitement for today. Kids, Carol brought back treats from her trip to Tønsberg," she called before leading her husband out of the room.
"You okay?" she asked once they were alone.
"He really thought — They all thought that Pete — that both boys were mine."
Pepper smiled and wrapped her arms around his neck. "Everyone knows how much you adore those boys, and they both are so much like you. It's not unbelievable that people might wonder. That's why I had the tests done."
Tony wanted to argue that, but found he couldn't, so instead he focused on what had been his biggest point. "They thought the only reason I would care about them was because they were mine. Peter thought that!"
"Oh, Tony." She pressed her face into his shoulder. "You know he didn't mean it like that. You know how self-deprecating he can get sometimes, kind of like someone else I know."
He huffed and she smiled up at him.
"He idolizes you. It's not that he thinks you wouldn't want to pay attention to him, he just doesn't think he's worth you paying attention."
"That's insane. That kid's amazing. We need to work on that."
"Pots and kettles," pepper mumbled before kissing his cheek.
I saw a post on Tumblr and had to write a thing. It was only supposed to be Harley at first, but then some of my MCU Young Avengers headcanons shoved their way in.