Just that they were cousins

Eren POV

"NO!" Mikasa screeched at Eren soon after he got home.

Eren, who as stated previously, had just gotten home, was incredibly terrified and confused.

"What do you mean 'NO!'?" Eren asked, shielding his face from a roll of toilet paper that Mikasa was throwing at him.

"I MEAN NO!" She yelled, pausing to grab another roll of toilet paper to throw, "YOU CAN'T MARRY A MAN YOU JUST MET!"

Ah. Ymir told her. Great.

"What gave you that idea, my beloved sister?" Eren tried to rationalize.

"YMIR SENT ME A TEXT WITH VIDEO, DON'T PLAY DUMB WITH ME, EREN!"

Oh shit. She said his name correctly, which means she's incredibly mad.

"What exactly was in said video, Mikasa..?" Eren asked, ducking to avoid yet another roll of toilet paper. Seriously, how much did they have?

Mikasa sighed, lowering her arm and pausing fire, "Eren, it showed that friend of yours, Levi, on stage asking if you'd marry him. Including your response. Has the movie 'Frozen' taught you nothing?"

Did she just compare real life to a Disney movie?

"Fair point, but have you ever seen the movie 'What happens in Vegas'? Besides, it's not like I have anything to offer- Not even good genetics since we're both men. Like, at least in 'Frozen' Hans would be getting a position of royalty, if anything I'm Prince Hans of the Southern Isles in this situation."

Mikasa raised an eyebrow at this, "How so?"

"Well, turns out he's the real Levi Ackerman, so he's loaded." Eren bragged, hoping maybe this would make his sister cool her tits.

Mikasa rubbed her fingers against the bridge of her nose, "Eren, I know you don't realize this, but that comes with it's own set of problems."

Eren crossed his arms in confusion.

"You'll bring in unnecessary attention wherever you go BECAUSE he's famous, plus you'll have more rich people etiquette expected of you, you'll probably have to lose the man-bun and dress better, need I go on?"

Before Eren could speak, there was a knock at the door.

"May I come in now?" Levi called, getting tired of his staring contest with a particularly large cockroach.

Eren slowly went to open the door, granting his steaming sister a sheepish grin as he did so.

As soon as the door opened, Levi barged his way inside, "To answer your questions, Mikasa, firstly he will not bring any attention to himself. Why, you may ask? Because only four people know who I really am, you two are included in that. Secondly, what do you mean by rich people etiquette? What about me screams snooty? I don't have a butler or a maid, just my assistant Petra who only does very little work around the house since I prefer to be the one to clean my own living space. Thirdly, he will NOT be losing the man-bun until the day I die, no matter what others have to say against it. Last but not least- who gives a crap about what he wears? Personally speaking, I love his AC/DC shirt and ripped jeans."

Mikasa and Levi stared at each other menacingly for what felt like forever, and Eren being himself had to narrate it.

"The Ackerman's, neck in neck for my affections, have entered in a very vicious staring contest."

Levi widened his eyes slightly at his comment and raised his head, "Hold the phone, I just realized we have the same last name."

Mikasa looked a little confused, "So?"

"There are only three thousand two hundred and eighty-three people in New York with the last name Ackerman, meaning there is actually a possibility we're related." He said, with a finger stroking his chin. Nobody questioned how he knew this information.

Eren pondered that thought, looking back and forth between the two. Raven colored hair, ivory skin, grey-ish eyes, both with Asian undertones even if Mikasa is outright Asian.

Levi seemed to be on the same wavelength as Eren, "Based on our physical similarities, I'd say there's an eighty-five percent chance we're related in a way." he concluded.

...

Now they were in a doctor's office, out of sheer curiosity regarding whether Mikasa and Levi were related.

Eren had fallen asleep, Levi was tapping his foot on the floor with his arms crossed and eyes closed in deep concentration, and Mikasa was picking dirt out from her nails with little interest.

As a Doctor emerged holding a clipboard with papers on it he was scanning through, Levi quickly backhanded Eren's bicep to wake him up.

"I'm up!" Eren quickly yelped from the slap, causing everybody besides Levi to give him a concerned glance which he blushed at.

The doctor sighed and looked at his papers again, "Levi and Mikasa was it..? I don't know why you came here so late at night with such a random request, but yes. You're related." he said, rubbing circles at the corners of his eyes with his thumb and middle finger.

"That's great and all, but how exactly?" Mikasa asked, looking up at him from where she sat.

"You're cousins." The doctor said blatantly.

"Elaborate, whose familial side got down with whose?" Levi pitched in.

The doctor looked at him exasperated. "My bad, it's almost 1 AM and some random Asians and a German guy walked in asking about familial relations because apparently one of the Asians is getting married to the German guy and needs to make sure he isn't related to said German guy's adopted sister because somehow that would ruin it."

"No, we're just curious because it's a weird coincidence." Eren smiled innocently.

"And because neither of us knew our family so finding out about them now is weird." Levi included.

The doctor sighed again, "Your uncle," he said pointing at Levi, "married her mother, and had her. Making her your cousin."

"Funny you say that because both of her parents are dead and I know my uncle is still alive, even if I haven't seen him in over twenty years." Levi said bitterly.

"Yeah, wasn't your uncle named Kenny? My dad's name wasn't Kenny." Mikasa added.

The doctor sighed for the third time, "Why did I move to New York... maybe, just maybe, if you don't know your family that well, you have another uncle?"

Mikasa and Levi groaned simultaneously.

They were cousins.