Sam, your identical twin (from another kin)

Throughout your years of schooling, you somehow managed to miss meeting a particular student: never having a class with them, never sharing a lunch period, and even never crossing eachother on the way to your next class. This somehow managed to keep up until your senior year. Things had gotten weird at that point, with multiple people referencing a sibling of yours in passing. Chris had started talking to you about movies and events you never went to, Joyce complemented you on missions you apparently took on for her, and weirder still, Nebula cornered you in the hall, angrily demanding to see the teleporter you use to warp around the school... actually, that last one might just been Nebula being Nebula.

Confused, you decided to sneak out of class early to talk to Chris. As you approached, you saw someone who looked exactly like you. Same haircut, same style of clothes, and even the same backpack slung over their shoulder. All that was different was their gender. You heard a voice that could be mistaken for yours, if not a slight change in pitch:

"Chris, I think someone is impersonating me, I'm really starting to freak out." Your imposter said, fidgeting with their backpack the same way you were doing right then.

Chris took a deep breath, as if she had been rehearsing for this talk for a while. "... Sam, I think they're just mistaking you for your twin... Look, I know your parent's divorce must be hard on you, but blood is-"

"My parents aren't divorced, Chris!" You and your doppelganger say in unison, before your doppelganger noticed you and screamed. "Chris, who the hell is this person?!?"

"...What? Yo-you're twins, right? Brother and sister, and your parents got full custody of one of you... Right?" Chris looked as if she was more shocked than the two of you.

"Chris, that's the plot of Parent Trap." You both say in unison again. This was really getting on your nerves, it was like there was an echo. Your doppelganger glared at you, as if they were annoyed too. If they were, they should have stopped copying you.

"Sam... Sams... you mean to tell me you guys are complete strangers?"

"Yep, never met this girl/guy in my life- quit copying me."

Chris tried to speak a couple times, pointing at both of you and making a weird wheezing noise. She eventually walked off without saying a word, breaking off into a sprint soon after. You and your doppelganger, after a bit more glaring, decided to settle this once and for all with a DNA test after school. On the walk to the local hospital, you and your doppelganger shared information about your lives. You discovered the following:

You and them had been living in the same place for your entire life.

Chris has been both you and your doppelganger's best friend.

You both were friends with, and are currently estranged from, Candy.

You both were informants for Joyce Barnes, secret agent 008.

Every time you ever saw that your username was taken and you had to resort to adding an "1" to the end, it was this fucker's fault.

Your doppelganger saw Nebula accusing other people of having a teleporter, so that one was just Nebula being weird as hell.

By the time you and them reached the hospital, you were very anxious; were you actually siblings? This person seemed exactly like you. Upon reaching the hospital, you were surprised to learn that the hospital could perform a DNA test instantly... Well, not instantly, but still, it was quick. After a minute of waiting, the results came in:

You and your doppelganger were completely unrelated.

You both sighed, in both relief and disappointment. Neither of you wanted to deal with the weird Parent Trap-bullshit being related to the other would entail. You both walked outside and shook hands.

"Well, that was freaky. Its nice to meet you Sam..."

"Nice to meet you too, Sam."

This was the start to a wonderful (and insanely weird) friendship...