A/N:So, to my knowledge, Supergirl has not yet shown up on Young Justice. As far as I'm concerned this means I get to use any Supergirl I want to. So this one is Kara Zor-El, Kal-El's biological cousin, and her characterization probably mostly closely aligns with the Smallville version of the character.

Set shortly after 1x05 "Schooled."

"You know I love you, right cousin?"

Normally when Kara tells Clark she loves him, it's with an indulgent sort of eye roll. Clark had originally thought that this was because Kara wasn't good expressing her feelings, but when Clark had finally straight out asked her about it, she told him that it just seemed so self-evident to her, that saying it out loud felt redundant. He was her only family left after all; she would love him even if he hadn't been, in her words, "the ridiculously nice guy who helped me when I finally landed on Earth."

Today though, when she said it, it was with a low warning sort of growl. A growl that makes it very clear that the unspoken second half to her statement was "But that won't stop me from kicking your ass."

Clark was larger, stronger, and more experienced than Kara. Not to mention that at twenty years old Kara might have her full array of powers, but they weren't all fully developed yet. Clark knew this. But none of it changed the fact that Clark would rather face down the unholy team-up of Doomsday, Brainiac, and Darkseid than an angry Kara, so Clark chose his next words carefully.

"What's wrong, Supergirl?" But not, it seems, carefully enough.

"Don't you 'what's wrong Supergirl' me, Kal-El. I changed you diapers and you will show me respect," she snapped.

All records Clark can find indicate that he was only a few days old when Krypton blew up, so he privately doubts that Kara actually changed his diapers. But he can't actually prove that she didn't so he pretty much just has to go with it whenever she whips that one out. "I'm sorry Kara," he said pacifyingly, "what was it you wanted to say?"

"I was saying that you're my family. And that I love you and I trust you. Do you trust me?"

"Of course I do," Clark reassured her. "I trust you with my life."

This, apparently, was The Wrong Thing To Say. "You know who else you trust with your life?" she asked him. "Batman. And Wonder Woman. And Flash. And Green Arrow. And The Atom. And Booster Gold. And every other member of the Justice League. I know you trust me with your life. What I want to know is if you trust me enough to tell me when important things happen. I need to know if you trust me enough not to keep things from me."

Clark still wasn't sure what had caused Kara's outburst exactly, but they'd seemed to hit on the underlying issue at least. Approaching her, Clark placed his hands on Kara's shoulders and looked her directly in the eye. "I might not always tell you everything, either because I don't think it's important or it's League business and I can't tell you. But if it's something that concerns you, then I will always let you know. You're my family Kara, and I don't want you to ever doubt that I love and trust you, okay?"

By Clark's estimation, and he was a fairly decent judge of the matter, that speech had been a pretty good one. Kara, though, did not relax like she was supposed to. If anything she got even stiffer, and her eyes narrowed. "So when I saw you on that bridge talking to a boy who looks just like you with our family crest on his shirt, was that League business?" Shit. "And when I overheard Black Canary talking about a Superboy, was that something that didn't concern me?" Shit, shit, shit.

He hadn't been trying to keep anything from Kara; he really hadn't thought the clone was something he needed to tell her about. But she had clearly gotten it into her head that he had been keeping the appearance of another Kryptonian from her. This was going to take some fast explaining.

"He is not from Krypton." Shock, good that would buy him some time. "Someone had set up a bunch of secret labs beneath Cadmus. Somehow they got a sample of my genetic material and they used it to clone him. He was made to be a weapon, someone with all my power, but under their control. Some of the kids stumbled their way in there and broke him out. Now he's part of some covert hero group with a bunch of the other kids. That's it. I wasn't deliberately keeping anything from you; I just didn't think it was important."

"You have a son and you didn't think it was important enough to tell me?"

"He is not my son!" Clark shouted. Bruce was bad enough; he did not need to get this shit from Kara too.

"Son, brother-"

"He's a clone!"

"I did not come here to debate semantics with you!" yelled Kara, eyes glinting red. "Is he or is he not of your blood and a member of the House of El?"

Clark wanted to say no. The kid wasn't his son or his brother or a member of his family in any way. He was a clone, one that Superman had and wanted nothing to do with. But he also didn't want to alienate Kara too much and she was dangerously close to coming to blows as it was. Really there was only one thing he could say to get out of this situation without a fight. "Yes."

"Good," Kara said with a nod, for all the world like Clark was a dog that had just performed a trick. He was the adult here, dammit.

"Now," she continued, voice low and measured, "where is he?"

Kara very deliberately did not fly as fast as she could toward Mount Justice. Just because she was angry at Kal-El was no reason to take it out on… Superboy.

Kara scowled. They would have to pick out a proper Kryptonian name for him. Her aunt had been considering Kon or Ten before deciding on Kal-El. Maybe Superboy would like one of those. Or if he already had a human name he liked then she could probably adapt it into a Kryptonian one as well.

By the time she had reached the mountain, she was only slightly angry. It must have still showed on her face though because when the three lounging teens spotted her they looked just a bit terrified.

Robin recovered first. "Hey Supergirl. You're not here to… kill Superboy or anything are you?"

"No," Kara snapped.

"Well if you just wanted to talk to him than I'm sure he'd be happy to see you," supplied the Martian girl – M'gann? – "He's in his room, down the hall, third door on the left."

"Thank you," Kara replied, before stalking off in the indicated direction.

She opened the door, perhaps not as gently as she could have. The boy behind it jumped, in seconds tense and ready for battle. At least, he was until he saw the crest on her shirt, at which point he dropped his stance in blatant shock. Apparently Kal-El hadn't seen fit to tell Superboy about her either. Martha will be hearing about this one.

For a second Kara wasn't sure how to proceed. She had been so focused on getting to Superboy, she hadn't really thought about what she would do now that she was here. On the one hand, despite living on Earth for over four years now, she was still more instinctually inclined to approach the situation like a Kryptonian, with a fair amount of formality and distance. On the other hand, Superboy was more familiar with Earth's customs and their incessant amount of physical affection. And based off some of the things Kal-El had said, it was likely that Superboy need some comfort.

Decision made, Kara crossed the room and swept Superboy up in a hug. At first he just stood there, but eventually his arms hesitantly came up and wrapped around her. She held on tight until she felt him start to shift uncomfortably, and even then she only pulled back far enough to put her hands on his shoulders.

"It's good to meet you, cousin."