Lord Yellowtail's Writing Room

Now, before you get the pitch-forks and torches out, I freely admit that in most versions of X-Men this would be horrifically disturbing, but Rogue and Kurt in Evo are both emotionally-damaged, attention-starved little messes that spend a very long time with no idea they're related to each other.

Further, they're not actually related to each other in any biological sense. Kurt is Mystique's son by blood-relation, and Mystique adopted Anna-Marie (Rogue) but never ever raised them together even for a moment. She didn't really even raise Rogue so much as she dumped her on Irene Adler. They never knew each other existed for the first 14-15 years of their lives. In Evo, their brother-sister relationship (while awesome and adorable and something I love) is basically a function of (1) Mystique screwing around with adoption paperwork to adopt a kid Irene's visions have told her will be useful weapon/tool later, and then dumping that kid on Irene; and (2) Kurt's superhuman ability to absorb anyone into his family and genuinely love them like they had been there the whole time.

So let's mess with that a little bit. It's not hard. Posit a couple of things:

1. Kurt gives up his crush on Kitty a lot sooner. They still end up being best friends, but he's a lot quicker to realize she doesn't like him like that and move beyond the over-enthusiastic (almost desperate) attempts to flirt with her. I get that he mainly did this (at least in my head-canon) because he was so desperate to be accepted by normal people and Kitty seemed the most normal person available (and was a very pretty, adorable person, too boot), but having watched the entire series has convinced me there is truly nothing there. Kitty was always devoted to Lance, even when she shouldn't have been, and they actually took time to showcase her flirtation/chemistry with Colossus at one point, minor as it was. In light of the whole series, watching Kurt try to flirt with her (and her almost-violent rejections of him) in Season 1 just makes me kind of sad.*
2. Kurt is still Kurt, and chivalrous and kind and willing to be friends even with those who are currently his enemies (at least, when he can tell they're not really evil), so without so much of his brainpower and attention focused on Kitty in Season 1 it's not hard for me to imagine him taking more notice of Rogue and interacting with her, if only to get her to leave the Brotherhood and join the X-Men.
3. Kurt is also a wanna-be Don Juan who only avoids being a bit creepy by being incredibly sincere, so it's not at all difficult to imagine Rogue actually starting to have a crush on him while she's still with the Brotherhood. Because Kurt is (insane enough to be) completely unafraid of her, and sweet, and is trying to be her friend even in the middle of Charles Xavier and Mystique's clandestine gang war, even though they're on opposite sides. (This is kind of how I feel the conflict in Season 1 comes off, to be honest, before things start to escalate and get more serious.)
4. Kurt, unlike Scott Summers--who is not only totally devoted to Jean Grey (even when he's in denial) but also sees the world in shades of red and probably can't even see blushing--is not completely oblivious to Rogue's interest and, amidst pleased shock and happiness, would recognize how rare and special an opportunity this is to have some sort of relationship, and gather up just enough of what little calm he possesses (when not enraged, which makes him eerily calm and dangerous) and manage to stumble forward just well enough to acknowledge her interest without scaring her off.
5. So by the time Rogue joins the X-Men, she and Kurt would have this undefined, flirty, almost-thing which is basically them being pleasant with and getting to know each other in the midst of an unspoken agreement to be just as in to flattening each other as the rest of the Brotherhood and X-Men seem to be.
6. Mystique is a bad mother who doesn't pay enough attention to her children for various reasons, so she is of course oblivious to any of this.
7. So Rogue finally defects and joins the X-Men and Kurt is so thrilled that he asks her (privately, with no-one knowing) on a genuine date-style date, and given their history of ... their thing, she accepts.
8. No one figures it out (because Rogue is an extremely private person and Kurt respects that) until they are quite solidly an item that everyone in the mansion is thrilled with (because neither Kurt nor Rogue are fun when they're being emo) and everything changes.

Xavier, of course, knew they were legally related the whole time but had no idea of their romantic entanglement, but Evo!Xavier has the bad habits of both holding back more information than he should (it's Dumbledore-esque!) and somehow not knowing crucial pieces of information about the people living with him while being the World's Most Powerful Telepath is kind of his jam, especially in the early seasons. Since they have no idea, he sees no point in wrecking their happiness and is genuinely pleased for them, even if it just makes him more piteous and aggravated at Mystique's poor parental skills.

By the time Mystique finds out, well...I would play the whole story completely seriously, but it's impossible for me not to imagine her getting extremely drunk and screaming at Magneto and Irene at least once. Not at the same time, of course. More seriously, when she tried to tell them she is their mother, they would probably just see it as some sort of incredibly sick and twisted plan to splinter the X-Men, and go on disbelieving her. Because as much as I like Mystique, her Evo incarnation was a terrible mother whose relationship with her children got destroyed when she got trapped in her own web of lies and rationalization. Hell, at one point she almost kills Rogue, and at another she basically feeds her to Apocalypse. Both Rogue and Kurt are arguably much better off being totally emotionally done with her in Season 1 instead of Season 4.

So that's a thing my brain came up with. Does this count as Lord King Badfic or not? I was never quite sure how that worked.

*I shipped Kurt and Kitty hard when I watched Evo, but in retrospect the show went out of its way to demonstrate just how much she was not romantically into him. She spends the whole series having what I personally consider to be an extraordinarily unhealthy relationship with Lance Alvers. I know I'll get some flack for saying that, because he changed and matured and stuff, but Season 1 still happened, and in Season 1 he tried to murder her parents once and tried to murder her and the X-Men several times. I can't really get around that no matter how much (dubious) character development you throw at him to improve his morals.