I love the twins in Appearances Are Deceiving. They're so similar and yet so different.
Both of them are the top students at Hornfel, they're tied for first and everyone knows they could never surpass each other, nor could anyone hope to surpass them. They're overachievers and perfectionists through and through, and if anyone even begins to think they could be better than them they will be swiftly and completely proven wrong.
Kairna and Taren were taken in by the school as young children when their mother died, and they decided they'd repay this kindness by becoming the best damn students the school had ever seen. Of course they both go about this goal in slightly different ways.
There's no doubt that both of the twins work incredibly hard, but Taren approaches every assignment, every test, and every mission with an easy smile and a confident attitude that frequently earns him the title of cocky douchebag. And to be fair to those who call him that, he does tend to like showing off, and has become a master of the humble brag. He doesn't let it go to his head though, and never stops pushing himself to be better.
Kairna on the other hand, when presented a challenge, becomes so determined that her focus is impossible to shake. She'll win even if it kills her, and doesn't think it's worth her time to convince herself that she can do it, instead opting to just do it. Unlike Taren, she's very rarely seen celebrating her victories, so Taren takes it upon himself to help her celebrate, usually in the form of drawing attention to her success that he's knows she doesn't want just to annoy her.
Taren is far more social than Kairna. He has a large group of friends and can usually be found cheating at playing cards with them at the nearby tavern.
Kairna is more reserved however, with a small, tight-knit group of friends, and she can generally be found reading in her favourite hidden nook in the library in her downtime, where only the librarian knows where to find her.
Taren is a go with the flow kind of guy. He welcomes change with open arms and is okay with going through his day without any semblance of a plan. Kairna can handle change fine as well, because you have to in this kind of environment, but she much prefers to have a routine and know what's about to happen.
Both are of course very good under pressure, but Taren tends to be quicker to act, whereas Kairna will try to quickly come up with a plan.
Neither are particularly trusting, but they go about it in different ways. Taren will be very friendly, even if he doesn't trust you, trying to figure out if he can, whereas Kairna will keep you at a distance, avoiding you if possible while trying to find out if you're safe.
That's all I got for now, enjoy!