Disclaimer: I only own the plot and my OCs. Anything you recognize as not mine belongs to Marvel Studios, Disney, and/or their otherwise respective owners.

Author's Notes: Ahahaha I had to type this up. If there are glaring errors, I apologize, I wrote this in the span of literally two and a half hours. But I had to write it, because once I started writing it I couldn't stop. Story title is from Sara by Fleetwood Mac, because The Chain just didn't really fit.

For my regular readers, dw, I'm almost caught up with the WIPs, just needed to take a break from them to do this.

Hope y'all enjoy,

~TGWSI/Selene Borealis

~within the wings of a storm~

In retrospect, Peter had always kind of known Mantis was his sister.

The story of Ego taking her in as a larva solely for her ability to get him to sleep had never made much sense. He had never questioned it, not to her and not anyone else on their team, not even Gamora, but he'd always wondered why his – their – father would take a child that he would have to take care of instead of a grown adult to do his bidding. An adult would most likely do everything in their power to leave, sure, but it wasn't like slavery was an unheard of concept in the universe. Yondu had been a slave for twenty years of his life, for example.

There had been an alien who had looked like Mantis, too, in Ego's portrait of him and all of his lovers. It'd been a blink and you miss it sort of thing, but it had been there. He'd just never thought much of it, couldn't think much of it. All too quickly they'd had to deal with taking Ego down, and his heart had been hurting the entire time because of the biological father he'd always wanted but would never have because Ego had killed his mom, and how Yondu had been that figure all along but was now dead, because he'd sacrificed himself for him.

"He may have been your father, boy, but he wasn't your daddy."

There hadn't been too much time after that entire mess to connect the dots, either. The Guardians had done their thing for a little while, as they always did. But then Thanos had began collecting the Infinity Stones in earnest for that stupid mission of his to halve the population of the entire universe, and Gamora, she...well, you know (he still couldn't think, much less say, the words, after all this time), and then he, Mantis, and the other Guardians sans Rocket and Nebula had been turned to dust. For five years, they'd been dead.

When they'd come back, there hadn't been time for him to think about Mantis, as horrible as it sounded. He'd been hurting, was still hurting, over Gamora. There was a younger version out there, sure, but she was and never would be hisGamora. Not that she had ever been his to begin with, but again, you know what he meant. The entire team was hurting over her loss, too, but for him it was different. Gamora had been the only person he'd ever bared his soul to in the way he had. She was the only person he'd ever wanted to spend the rest of his life with, even though in their line of work that didn't exactly mean much. And now she was –

You know.

But just because he'd never consciously connected the dots didn't mean some part of him hadn't known. He and Mantis, they didn't look like each other. Their mothers were two completely different species. They didn't act much like each other, either. But they had a connection with each other in a way which was...different, not any better or less than, just different, from the rest of their patchwork family. Peter understood her longing for a family, having always had the same secret desire himself, and why she'd wanted to stay with them instead of forging her own path after Ego. She understood him, plain and simple, even without her empathy powers.

Gamora had remarked on it, once. "You two seem to operate on your own wavelength," she'd said one night, when they'd been curled around each other in their bedroom on the Benatar.

"Is that a bad thing?" he'd asked.

She'd shaken her head. "No, it's just interesting."

(Had she known, he wondered? It wasn't like he could ask her now. But a part of him liked to think she had. Not that she'd ever needed any strings attached to her love, but after Ego she'd welcomed Mantis into their family with open arms, when while they'd been on him they hadn't really gotten along at all.)

After Gamora, Mantis had situated herself as the one in charge of helping him with his grief. Nebula and Rocket, they'd understood where he was coming from, but for them they'd already been grieving for her (and the rest of them) for five years. They still grieved for her, too, but their hurt was old. Not fresh and painstakingly new like it was for him, Mantis, Drax, and Groot. And Thor, of course, the asshat, hadn't been much help at all.

(He knew he was being cruel with that statement. Thor had his own grief to bear, after losing his mother, his father, his sister, his planet, his brother, and then half of his people. But it was easier to pretend to dislike him, than it was to admit that he actually cared about the god.)

When Peter had stopped eating because his grief had swallowed up his stomach, it had been Mantis to intervene. "Please, Peter," she'd said on more than one occasion, looking at him with mournful eyes and a sad smile as she'd held a plate of food in her hands. "You're losing a lot of weight. Please eat something."

Other times, she hadn't asked him to eat at all. She'd merely come over to wherever he was on the ship, or whatever planet they were on, or on Knowhere, with two things of food in her hands: one for him, one for her. They'd sat down together and ate. Sometimes they'd talked, other times they hadn't. Regardless, she'd been a balm, a solace in his agony of pain.

When he'd woken up from a nightmare of imagining how Gamora had died, or watching her turn to dust in front of his eyes like he had, or watching Mantis and Drax turn to dust all over again, Mantis had been there for him. She hadn't tried to lull him to sleep like she had Ego; instead, she'd held his hand or put her head on his shoulder, or even hugged him. "I have bad dreams too," she'd whispered one night. "Of Ego and his children. Of him killing them. I could've helped them like I did you."

"There's nothing you could have done," he'd tried to argue.

"No, I could have," she'd disagreed. "But I am thankful I got to help you."

The others had tried to help him too, of course, but with Mantis it had been different. It was always different. There was an undercurrent to whatever she did when it came to him, an edge.

And now he knew why. He'd always kind of known why, he realized, he'd just needed her to connect the dots for him.

She was his sister.

He wasn't kidding when he told her that her telling him was "the best Christmas gift I could ever get." He wasn't holding back when he hugged her, either, and she him. Lately, he always felt cold; it wasn't an external thing, but an internal one, as all the grief and pain he'd been and was experiencing seemed to lower his body temperature as well as his mood.

But Mantis, she was warm. She felt more like home than Earth ever would for him now; she felt like lazy days on the Eclector back when he'd been a kid, with Yondu threatening to kill him and eat him because he'd never really meant it and it'd been his way of showing his love. She felt like them before Thanos, when it had seemed like nothing could ever hurt their patchwork family and they'd always be together, no universe-ending threats or five years of being dust to separate them.

And she'd done all of this for him. She and Drax had gone to Earth to get all of the Christmas stuff for him. They'd kidnapped Kevin Bacon for him – and yes, he would be having words with them later about that and why it was wrong, but he could appreciate the meaning behind the action if not the action itself. Because she was his sister, and she'd wanted to "save" Christmas for him, not knowing it'd never been ruined in the first place.

("Merry Christmas, Mantis."

"Merry Christmas, Peter.")

As they pulled away from each other, however, he knew one thing. Peter saw the relief on her face that he'd accepted her, clear as day, but he also saw her grief. Her loss. "Mantis," he said slowly, watching another tear fall down her face. "You've been keeping this secret a long time, haven't you?"

It was a rhetorical question, obviously. He knew the fact was true.

She nodded anyways. "Yes," she whispered. "I didn't want you to hate me."

He smiled, despite how her words made his heart ache. "Oh, Mantis, how could I ever hate you?"

"Our father – " she began.

"You're not Ego," he replied. He remembered his own struggles with coming to terms with their father. "Ego was a horrible person, but you're not, Mantis. You're one of the nicest, goodest – " that wasn't a word, and she knew it, the edges of her mouth curving upwards slightly " – people I know. You could never be like him."

Her smile was gone as soon as it'd appeared. "Our siblings – "

"You couldn't have saved them," he interjected.

"I could have," she responded. "I could have put our father to sleep for a long time when I was old enough. At least one of them, I would have been able to – "

"And where do you think you would've ended up?" he returned. "What do you think he would have done?"

She did not say anything, as she clasped her hands together nervously.

He gripped her by the arms. His touch was neither hard nor firm, but as he looked into her eyes, he wanted to make sure he was touching her. To ground her to this place and time, instead of letting her swirl further into the drain of "what if's"and "could have's."

"He would have killed you," he stated. "You know he would have. He considered any kid who didn't have his powers 'failures.' The only reason why he kept you alive was because of your own gifts. But if you inconvenienced him, he would've killed you. And then where would we be?"

Her lower lip trembled. "Peter – "

"We would be dead, too." He was confident in his belief. It didn't even occur to him he could have been wrong. "Ego would've killed us, all of us. And I wouldn't ever have gotten to know you. I wouldn't ever have known what a badass sister I have."

"You could have survived."

"Nuh-uh. Nope," Peter said. "You're my sister, Mantis. I wouldn't have it any other way. You're the only one I'll ever need. And if you don't believe me, feel it."

He lowered one of his hands, holding it out to her. Gingerly, she accepted it. As her antennae lit up, more tears followed the paths of her first two. She started to cry in earnest, sniffling, as he poured his emotions through the temporary bond, showing how much every word he'd spoken was true.

"There, you see?" he questioned rhetorically. "I love you." He didn't mention how hard it was for him to say the phrase, never having grown up with anybody telling it to him, never having told it to anyone except Gamora. "You're my sister. Ever since...ever since Thanos and Gamora, you've looked after me. You did all of this Christmas shit for me, because I know you love me, too. But I know you've been hurting, to keep this secret so long. So let me be there for you, Mantis. It's my turn to look after you."

Sobbing openly, she wrapped her arms around him, pulling him back into a hug. Gratefully, he reciprocated.

Before the Guardians, before their patchwork family, he never would have thought about saying or doing this with another person. It hadn't been his family's – Yondu's – way of showing affection. But he knew it was right, because he felt it in every inch of his bones. After all she had done for him, Mantis deserved for him to do the same with her.

"Come on," he said after a little while, once her crying had settled down into something more quiet. He tucked a lock of hair which had been tugged out from her headband back behind her ear. "Let's go get some hot chocolate, just me and you."

Word Count: 2,088