THE EVOLUTION THEORY

Disclaimer: I don't own the X-Men universe and am not profiting from this work.

CHAPTER ONE

"C'mon, we're going to miss the commencement speech if you take any longer!"

Rolling her eyes at the slightly panicked call from somewhere downstairs, Ana did her best to twist her hair into a casual bun at the back of her head and failing miserably for the twelfth time. She intended for her hairdo to look informal but groomed, instead of the unkempt mess it kept turning into. Silently cursing Raven for always being able to pull off the casual and pretty look with such ease, the slightly frustrated girl eventually gave up and just pulled her blonde locks up into a ponytail.

Giving her appearance another quick perusal in the full length mirror next to her dresser, she turned and bounded out of the bedroom and towards the large staircase leading towards the foyer, taking two stairs at a time.

"Took you long enough, Ana. Really, I just can't wrap my mind around you girls and your obsession with your appearance."

Heading out the front door, Ana stuck my tongue out at her brother, who had been impatiently waiting for her on the threshold. "Well, lucky for you then that you didn't pursue Behavioural Science, otherwise we wouldn't be on our way right now to see you get handed your PhD."

"Very funny, Ana, you're slow and hilarious. Now get in the bloody car," Charles nearly growled, motioning towards the driveway where Raven was already behind the wheel of her Beetle convertible. They both climbed in, Ana folding herself into the backseat while Charles seated himself in the front next to Raven. "If I'm late because of your insufferable vanity, I swear to god, I will throw out all your make up and creams and whatever rubbish you insist on wasting time on before stepping foot outside the door!"

Gasping in outrage, Ana glared proverbial daggers at the back of his head. "You wouldn't dare."

"We'll find out soon enough, won't we," he threatened, before giving a surprised yelp as the girl leaned over to pinch his elbow through his suit jacket.

Raven had already driven them out the front gate as she gave a loud groan and threw stern looks at both of her sibling, one through the rear-view mirror. "Cut it out, the both of you. I've had enough of your bickering for today." And she meant it, having already suffered through an entire morning of taunts being thrown back and forth all the way through breakfast.

Luckily, her scolding had its desired effect and both quieted down, only huffing in irritation as they turned to look out of their respective windows. Honestly, the effect these two had on each other, reverting back to petulant pre-schoolers. She loved them both, both it drove her mad at times.

The rest of the drive to Oxford was made in silence, only broken by Charles as they found a decent parking space and his excitement about the upcoming event once more shined through. "I can't believe I'm finally graduating," he breathed, a small smirk tugging at the corner of his mouth. "Goodbye student life, hello Professor Xavier."

Making their way towards the Sheldonian Theatre where the graduation ceremony was being held, Raven walked in between her brother and sister, throwing her arms around both of their shoulders.

While she was nearly Charles' height with her high-heeled boots, it was considerably easier with Ana, who was only a mere five foot five in just her flats. "Ready to give your grand speech, Professor?" She teased, giving his shoulder a little squeeze.

He grimaced slightly at that, suddenly reminded of having been given that specific honour. "I hope I don't botch it up because of nerves, that would be embarrassing. Set the tone for the rest of my career, most likely."

"You, nervous? Pff," Raven tried reassuring him, voice full of confidence. "Besides, if you do get nervous, I heard that picturing the audience naked helps." Then, thinking on it more, she pulled a face. "Except for the faculty, of course, because... ew."

Charles had begun to chuckle, before Ana cut in with a sideway smirk. "Shouldn't be too difficult for Charlie, since he's already seen most of the female grads naked."

This had both girls snickering, while he chose wisely not to comment on her rather astute remark. His sisters never missed out on an opportunity to tease him on his luck with the ladies.

The rest of the day passed by rather quickly, with the girls watching the ceremony patiently only to whoop and holler embarrassingly as their brother finally rose up to accept his degree. Before long, they were walking out the door again, on their way to celebrate the occasion in a more alcohol rich fashion.

The bar was rowdy and packed with graduates, all letting loose without reservation, and Charles, for all his manners and class, wasn't any different. With Ana and Raven getting another round of drinks at the bar, they only shot the young man amused glances every now and then as he was attempting to chug down a ridiculously large pitcher of beer while some of his friends egged him on. If they noticed the dark-haired woman approach him purposefully, they unconsciously dismissed it as a result of their brother's apparent, inexplicable pull to women and simply returned to their own drinks.

"Which one?" Raven inquired, voice hushed even though nobody would be able to overhear them over the loud ruckus in the establishment. Leaning over the bar somewhat, careful to avoid knocking over their glasses, Ana pointed to a group of guys at a table in a corner of the pub.

"The tall one, right next to the one with the unibrow over there."

"The blonde one?"

"No, the one with the green jumper and shit-eating grin."

Ana watched as the guy in question once more ogled her sister and Raven actually took notice this time, immediately turning away from the cute, young man that was openly flirting with her. Raven's faced flushed a bright red, eyes darting over to her sister nervously. "Oh shit, he saw me looking."

Rolling her eyes, Ana took another long gulp of her drink. "That's kind of the point of eye-fucking someone across the room. No fun if the other's not participating, right?

"Ana!" her sister exclaimed, slightly scandalized at the crude language but unable to stop a grin from forming all the same. "He is, though, isn't he?"

Nodding seriously, the younger of the two, if by age only since Raven didn't look a day older than her sister thanks to her mutation, Ana replied, "Oh yes. In his head, you've already reached second base and are quickly approaching third." Acting as if she shared Charles' telepathic abilities, she once more looked over at the guy for a couple of seconds before raising her brows in mock appreciation. "Quite the cunnilingus expert, that one."

Raven gave a surprised bark of laughter at the other girl's antics, trying to surreptitiously turn to catch another glimpse of the young man when Charles suddenly appeared behind them. Both girls immediately took notice of his grave expression, clouded as it was by his obviously inebriated state. "We need to go. Now."

Surprised, they were ready to question their brother about his sudden mood swing when they heard his voice inside of their heads, mentally pleading with them to just listen to him for once without asking questions first. 'I'll pay for the drinks, please go bring the car round.'

Prone as Raven was to following Charles' commands, she immediately picked up their coats and headed for the door while Ana eyed the dark-haired woman standing behind her brother with suspicion. She was, without a doubt, responsible for cutting short their night of celebration, but the young girl couldn't phantom what she could've said to get this kind of reaction out of Charles.

Opening her mouth to object and demand an explanation, Ana was silenced by a quick look from Charles. She knew that look, and it never foretold anything pleasant. Opting to actually take heed of her brother's words for a change, she settled for simply throwing the unknown woman a dark look before trailing after Raven.

As soon as Charles climbed into the car and told Raven to drive straight home to pack their bags, they unleashed a whirlwind of questions on him, completely flabbergasted with his behaviour.

Whatever they had speculated prior to his arrival didn't even come close to what he proceeded to explain to them.

The woman was a CIA agent and wanted to fly him out to their headquarters in the States to consult on a case that involved a terrorist organisation which included a number of possibly mutated individuals? Could he repeat that, because they must not have heard him correctly? Or the woman had drugged him and was playing a prank on him that, honestly, was far from funny.

"While I may've had a few drinks-" Ana snorted, "I am still of sound enough mind that I can assure you that this is no joking matter."

"You don't need to tell us! Raven might've finally gotten laid tonight if you-"

"And," he continued on firmly, intently ignoring both the interruption and the reference to his sister's sex life. "Agent McTaggert will have a plane ready to leave for Virginia within the hour. We are to pack some clothes and essentials before meeting up with her at the airport."

Both girls exchanged looks in the rear-view mirror, realization finally dawning on them that this might actually not be some elaborate prank. "Well... damn," Raven muttered, stepping on the gas a bit harder now that the seriousness of what was happening sunk in.

"Terrorists as in real life terrorists?" The other blonde asked uncertainly, voice still slightly sceptical. "Like assassinations and bombings and evil masterminds plotting all of our deaths terrorists?"

Charles simply turned his gaze out of the window instead of responding, which was all the answer she needed.

"Well... damn."

A/N: While this might be quite a fanfiction cliché, one of the main characters suddenly having a sister, it serves the purposes of this story perfectly. I'm aiming to not go the MarySue route, of course, and as she's going to be one of the youngster's in the story, she'll have enough behavioural issues as the rest at that age. She will, for all intents and purposes, be a properly irrational teen at time and an annoying younger sister ;).

I just adore how Charles and Erik are portrayed in First Class, but most fics are slash (for obvious reasons, because hot damn…!) and I was just in desperate need of some Erik/OC hotness. Unfortunately, there are only a few of those drifting around , so I decided to start writing one myself. I've already written quite a few chapters, but was hesitant about publishing them online till now. Here we are, though! Hehe. The first chapter can feels quite rushed, I apologize, but the pace will even out as the story progresses.

You can find a link to the banner/fanart for this story in my bio.

Let me know what you think! Constructive criticism is more than welcome, of course!