Important note: Peter was not in any Avengers movies, takes place after Infinity War, every superhero lives together, Peter is a baby, but he already has his powers. He's about the same age as Luna as of this point in the story. Peter lives with the Avengers.
Also, you will need to know what the show, LEGO Elves: Secret Of Elvendale. Here's a brief description, and you must read this before you read the story. It helps you understand.
So basically, there's this place called Elvendale. You can only get there from Earth by using a portal that your amulet makes. There are elves that live there, along with goblins and dragons. The elves you need to know about are Air, who can control air, Naida, who can control water, Farron, who can control earth, and Azari, who can control fire. There's also a human, who's name is Emily. She wills he explained later. Now, to the story!
"Tony? There's… someone in the lobby, waiting for you. You need to get down here." The lobby worker for that night said. Tony rushed downstairs. He saw a woman with a baby.
"Tony Stark, you need to help this baby." The woman said. Tony gestured at the lobby worker. She called down he rest of The Avengers. They came down, and were confused by what they saw.
"Guys, she wants me to take care of this baby." Tony said. Pepper was confused.
"Why?" Pepper asked.
"She's… special." The woman said.
"In what way?" Steve asked.
"Uh, She has powers. We don't know what, though. It skips a generation in my family. We don't know how to take care of someone with superpowers." The woman explained.
"So, you want us to take care of her?" Tony asked.
"Yeah." The woman said.
"I'm on board. When she grows up, she could be a new team member." Steve said.
"I'm on board." Natasha said.
"So am I." Clint said.
"I'm fine with it." Pepper said.
"Sure." Bruce said.
"I'm good with it." Sam said.
"Me too." Bucky said.
"I am also fine with it." Thor boomed.
"Tony? That leaves you." Steve said.
"Alright, well, I'll take care of her." Tony said.
"Tony, we'll take care of her. Not just you." Bruce said.
"What about Scott? Do you think he'll be fine with it?" Natasha asked.
"Yeah, I mean, he had to deal with Cassie as a baby, I had to deal with it. We can help you because we know a thing or two." Clint said. It was too bad Vision and Wanda lived in their own place. The woman handed them the baby, and necessities, like food, milk, and a stroller, to start them off. She also gave them the birth information. The girl was born on January 6th. The girl also had an amulet on. It was a pretty blue color.
The Avengers decided to name her Luna, because of Luna from Sailor Moon. She looked like the human form of Luna, with a crescent moon birthmark, blue eyes, and long, dark hair. Her birthmark was on her forearm, but it was still a crescent moon birthmark. She had pointed ears, and everyone thought it was a deformity. Little did they know that her pointed ears weren't a deformity, but she was something else.
Luna knew she was adopted. It was obvious. Scott was a little mad he wasn't consulted, but he liked Luna. She was awesome. Peter loved her. He thought she was adorable. Everyone loved having her around. She didn't even cry that much. Only when she was hurt, which was very rare. When she needed food, or a diaper change, she would clap her hands.