The reason Kate and Eli do not work together in a relationship is because they are both characters with this desperate, clawing need for control. It is the reason they even end up fighting for control over the Young Avengers and why they end up as co-leads but continue to fight and bicker and pull for full control regardless. Personally, I don’t really acknowledge the park incident in Young Avengers Special #1 (2005) as part of Kate’s canon, simply because it’s the backstory for EVERY comics woman (wonder why 😐) and it isn’t even an interesting choice for her or her motivations and it has absolutely no impact on her character to the point where I’m not even sure most people will know what I’m talking about, but if you do, it can totally be used as reasoning for why Kate has this need for control over the people and situations around her. And even if you don’t have a clue what I’m referring to, or simply don’t acknowledge it as canon, even without that Kate is SUCH a character than is obsessed with control, ESPECIALLY as a teenager in that first Young Avengers run. She wants to understand the motives of everyone around her, and use that to her advantage so that they do what she wants them to. She hijacks Eli’s plans every chance she gets to implement her own that she believes are better simply because she can control how they play out. She uses the people around her and will manipulate situations until she is the one calling the shots because she thinks she can do it best. And Eli… is the biggest control freak alive and then some. He needs to be able to see and understand and control the actions of everyone around him because he thinks that is the clearest path to success. He wants everyone to act the way he wants and take the actions he wants, and whenever people (Kate, Tommy, Billy) push back against that he reacts explosively because to him his control of a situation is what will lead him to doing good and being a good person. Eli’s relationship with the idea of goodness and morality is really its own separate post, and one I could very well make, but I’ll just say that the reason Eli needs to have control so bad is because he has this underlying obsession to never stray from the perfectly moral path and he’s the only one that can keep him on that track and if anyone else has control over the situation they can drag him off it. (Which is why he reacts so badly at the end of Children’s Crusade, but that’s not the point rn.)

All this to say, Eli and Kate are both characters who NEED to be in control of their situation and the people around them. It’s compulsive for them. And when you put them together, they cannot have that. It’s this constant balancing act between the two of them that fosters this enteral fight between them that neither of them can win and it leads to them hating each other, especially when they love each other. They cannot last as a couple on their own because they will always try to gain control and a level of security over the other person because it’s just what they do.

Which is WHY, if you were to add a third person into their relationship (Tommy specifically, but I’ll get to that in a second) this problem… well, it doesn’t disappear, but it does become significantly less of an issue. Because then they can both still feel in control, and not threatened, and keep their level of security without having to break down the other to do it. It alleviates the pressure of positive feedback loop of mutual destruction by placing it off of themselves. And the reason it should be Tommy specifically is because he would let them. First off because he is a person who kind of picks the path of least resistance and accepts other people’s choices and ideas kind of without much care, because it’s easy and more importantly safe, and again Tommy is an abused kid who grew up in an unstable environment and had all his safety stripped away from him and that fact impacts every action he takes, so having that sense of safety is important. And having that relationship with Kate and Eli WOULD provide that sense of safety because it’s essentially giving him a layer of security through the idea that there is this path he can take that will ensure his safety and his role on the Young Avengers and it isn’t even hard. Not that he would listen to them, or even let them boss him around— it’s Tommy, his favorite thing in life is being ornery and pissing people off just for the heck of it —but he would have the choice, and as long as he’s letting them without pushing back too much or, more relevantly, trying to force his own brand of control on them, Eli and Kate wouldn’t really be affected in any way more than annoyance at his refusal to play along. Because he is playing along, and the pushing back is part of that.

“You aren’t wearing that,” Tommy says firmly, arms crossed. Eli frowns, tugging at the collar of his shirt.

“Why wouldn’t I?”

“Because,” Tommy insists, like that’s an explanation. “Kate, tell him he can’t wear that.”

Kate sticks her head out of the bathroom, hair half-curled and spilling over her shoulders. “I think he looks good,” she says with a shrug. Tommy scowls at her.

“You think he looks good in anything.”

“I think he looks better in nothing,” Kate teases, throwing him a wink before disappearing back into the bathroom. “Don’t you?”

“Don’t turn this into a sex joke,” Tommy threatens, which is bold coming from the boy Eli is fairly certain can and will turn anything he hears into a sex joke. “Eli, you can’t wear that.”

“Why not?”

“Because!” Eli stares at him, and Tommy throws his hands up with a groan. “You look like a nerd.”

“A nerd.”

“You look, like- stuck up.”

“Stuck up.”

“Stop repeating what I say,” Tommy hisses. “You look like a preppy douche.”

“What does that even mean?”

“That you’re a preppy douche!”

“A pretty douche!” Kate calls from the bathroom, and Tommy flips off the open bathroom door despite the fact that she can’t see him in the slightest.

“Okay,” Eli says. “So I’m a preppy douche according to you. What does that have to with my outfit?”

“It means we’re going clubbing, Eli, holy shit.”

“…and?”

“And you can’t wear that clubbing!”

“Why not?”

“Because you look like a preppy fucking douche!”

Kate comes out of the bathroom thankfully before Tommy can resort to murder, wrapping an arm around his shoulders and pressing a kiss to his temple. “Baby, please remember that if you murder our boyfriend it’s going to royally screw up our evening plans.”

“I’m not going to,” Tommy huffs, extremely unconvincingly. Kate laughs, glitzy earrings bumping against her jaw.

“Go get ready, I’ll help him.”

“I don’t trust you either,” Tommy complains, turning his head to press his face against her curls. Eli reaches out to smooth a hand down Kate’s arm, just because they’re touching and he isn’t and he wants to. “You dress…” Tommy trails off, waving a hand. “Rich.”

“I am rich,” Kate says dryly.

“It shows.”

“Just go, Tom, it’s not like you’re making any progress here.”

He groans, loudly, then grabs the front of Eli’s not-approved-for-going-out shirt, kissing him quickly before doing the same with Kate and proceeding to flip them both off, kicking the bathroom door shut behind him as he leaves.

“Asshole,” Eli says, not really at either of them but just to say it because it’s true. Kate giggles, pulling the hem of his shirt and guiding it off him. He lets her, because it’s Kate.

“He’s not wrong,” she says. “You do look very… well, you look like a teacher’s pet. It’s not exactly the vibe.”

He throws his shirt on the bed, crossing his arms over his bare chest. “Oh, really? What is the vibe, then?”

“Y’know.” She grins, her glossed lips pulling over her teeth. “Sexy. A little slutty.”

He raises an eyebrow. “Right.”

She adjusts her shirt pointedly, a deep-cut purple tank that goes down to at least the bottom of her ribs and doesn’t cover much more than that, considering the back is all but nonexistent. “A little slutty,” she repeats, smug in the way his eyes lock in on her chest— how’s he supposed to not, she’s right there and she’s gorgeous. “It’s what makes it fun.”

He drags his gaze back up to her face, frowning. “Kate, you wear a crop top and Tommy runs around in full spandex. How much sluttier do you want?”

“It’s not spandex, dumbass!” Tommy calls from inside the bathroom, and Kate smirks.

“Does it matter what it is?” She lowers her voice, leaning in with a conspiratorial grin. “Makes his ass look great either way.”

“I heard that, Katie!”

She laughs, then grabs Eli’s arm, pulling him towards the closet. He waits for her to tell him what to do next, standing there as she hums at the closet, lips pursed and hands on her hips. “He does look good,” he says, mostly because it’s true. “It’s annoying. And distracting.”

“Right? Nothing makes me miss shots like him, I swear.”

Eli shrugs. “You aren’t too much better. Crop top, remember?”

“You have killer abs!” Tommy helpfully adds through the door, and Kate smiles wryly.

“Aww, you two are cute. Eli, put this on.”

He wrinkles his nose at the piece of fabric she hands him, holding it out in front of him. “Kate, I don’t think this is even clothing.”

“Don’t be difficult, hon.”

“I’m not. I genuinely don’t think this is a piece of clothing, I think you just handed me the gaudiest fabric I’ve ever seen in my life.”

Kate rolls his eyes, gesturing him towards the mirror as he pulls the shirt— shirt? —on, frowning at himself in the glass.

“The slacks can stay,” Kate decides, draping herself over his shoulder. He stares at her in the mirror.

“Great. Have you seen the rest of it, though?”

She snickers, running her hands down his biceps. “It’s hot.”

“It’s really not.”

“Your chest is out. That’s hot, at least.”

She’s not wrong, it is. The shirt only has buttons up to the bottom of his ribs— look at that, he and Kate have the same look going on, isn’t that cute —but the real problem is the gaudy, satin-y material in a shiny pearlescent color that pulls tight over his muscles, nerve-wrackingly promising to tear if he moves wrong. “Where did Tommy even get this?” he wonders out loud, and Kate smacks his shoulder.

“That’s mine, actually, thank you very much.”

“Where in the world did you get this?”

She ignores him, going back to the closet before returning with a handful of jewelry which she drapes over him artfully without letting him get a word in otherwise. She slips a few bracelets on each wrist, the sleeves pushed up his forearms, and slips at least three necklaces, all varying degrees of attention-grabbing and over the top, around his neck before she reaches up. He catches her wrist, frowning.

“Kate, I don’t have my ears pierced.”

“They’re clip-ons, duh,” she says, rolling her eyes and clamping the dangly pearls on. He stares in the mirror suspiciously, lips pulled down.

“I look… gay.”

“You are gay,” she reminds him sweetly. “You have sex with men, that makes you gay.”

“One man,” he says, like that’s an argument. Tommy cackles from inside the bathroom, sounding smug.

“Yeah, Katie, it’s just me! Cause I’m just sooooo special, right sweetcheeks?”

Eli shudders. “Never call me that again.”

“Sunshine? Cupcake? Snookums? Babydoll?”

“Baby- you’re half my fucking size, Tommy, what do you even mean “babydoll”?”

Tommy gasps, offended, as Kate quickly covers her laughter with a cough. “Half your- okay, asshole, how ‘bout I-“

He doesn’t get any further than throwing the door open, though, because he freezes, eyes wide as he takes Eli in.

“Shit, Kate, you actually did it. I’m shocked.”

Kate puts her hands on her hips, fingers splayed over the enticing strip of skin between her low-rise jeans and her top. “I know, I’m a miracle worker.”

“You should take that all off,” Tommy says, still staring. “Let’s stay in. We should have sex. Don’t you guys want to have sex?”

Kate rolls her eyes. “We can have sex at the club, baby.”

“I’m not having sex in the club bathroom,” Eli says quickly. Tommy shrugs.

“I will.”

“I know you will,” Kate tells him. Tommy grins, like having sex in a dirty bathroom stall is something to be proud of. Then again, it’s Tommy Shepherd, so maybe it is for him.

“You look good,” Eli says, mostly so that the conversation moves along and Tommy and Kate aren’t given the opportunity to try and talk him into having sex in the club bathroom. “And you, Kate, obviously, because I didn’t say it earlier.”

Kate flicks her hair over her shoulder, looking smug. “I know I do.” She drags her gaze over Tommy, grinning. “You do look good, though, baby.”

He rolls his eyes at the pet name, but strikes a pose for them anyway, sticking his tongue out between his grinning teeth. “I always look good, for the record, but it’s nice hearing it.”

The cropped shirt rides up well over his stomach, over his pecs when he lifts his arms like that, and Eli steps closer so he can run his hands over the skin, Tommy giggling slightly at the touch.

“There’s so much glitter on your face,” he says, because that’s less embarrassing than admitting he wants to run his tongue over the sharp planes of Tommy’s stomach.

“I know,” he says. “And just think, later tonight it’ll be all over you, too.”

“Hot,” Kate offers.

Eli frowns. “And also impossible to get out of the bedsheets.”

“So you do want to have sex!” Tommy crows, and Eli pinches his side.

“I meant sleeping, get your mind out of the gutter.”

“We’re going to a club, dude. The gutter is exactly where my mind should be.”

Eli kisses him, just to shut him up. “Are you running us there?”

“It’s a nice night,” Kate interjects, leaning over his shoulder to kiss him and Tommy in quick succession too. Her lipgloss leaves shine against their skin, and her hands join Eli’s, tracing the lines of Tommy’s bare skin. “We should walk. It’ll be fun.”

“Great,” Eli says dryly. “So even more people will see me in this outfit. That’s great. I love that.”

“We’re going out, hon, people were always going to see you.”

“Nobody sees your clothes at clubs,” Tommy interjects. “Everyone’s too busy at trying to see what’s underneath.”

Eli, who has been doing a remarkable job at not being controlling if he does say so himself, tightens his grip on Tommy’s waist possessively. “They better not.”

Tommy’s lips quirk downwards. “If that’ll make you uncomfortable, dude-“

“Tommy,” Kate interrupts. “He isn’t uncomfortable. He’s jealous.”

Which is fair. Because he is. If he had to rank “other people thinking about Tommy and Kate the way he thinks about Tommy and Kate” he’d place it roughly between getting killed and the world ending. Because they’re his, actually, and he’s of the opinion that no one else should get to see them, maybe ever. Luckily it’s an opinion that the two of them think is hot, because he also knows it’s controlling as hell. But.

“Oh.” Tommy blinks, grinning. “Oh,” he repeats, pupils huge as he kisses Eli again, messier this time. There’s already glitter on his face now, Eli is sure. “That’s hot.”

“Right?” Kate purrs, hooking her thumbs through the loops on Eli’s pants. “Hm. Maybe we shouldn’t go out tonight.”

“Both of you, off,” Eli instructs, stepping away. “We’re going out.”

“Do we have to?” Tommy whines, and Kate pouts, lips plump.

“Eli…”

“God, you two are terrible,” he huffs, running a hand over his head. “Okay, well, I’m going to the club now. If you two want to miss it-“

“Absolutely not!” Tommy yelps, appearing at Eli’s side with their arms looped together and his hand wrapped tightly around Eli’s bicep. “We’re going, we’re going.”

Kate pulls the door open, remembering at the last minute to grab her bag. Which is good, because it’s got their key, and they should really stop breaking in to their own apartment. “So, Eli. Bathroom sex when we get there?”

“I’m regretting this already.”

“I’m joking, I’m joking. Tommy-“

“Oh, totally.”

“Sweet.”

“Stop that, both of you, or I’m leaving.”

“Okay, fine, sex at home like lame people. I hope you’re happy, hon.”