Yin and Yang aren't brothers. They're formed by an experiment from a different object show (BFB lol) where two random balls, black and white, got fused together into a Yin-Yang symbol and that symbol came to life. They eventually escaped and then participated in II. Yes this is a kind of BFB and II crossover but I like it.

Yang can be cruel and a real douche, but he can be a cute cinnamon bean without realizing. Yin is mostly cute, but can be a savage without realizing.

When someone says something about Yin-Yang being cute, Yin will blush and smile, saying "Thank you!" or something like that, Yang will deny it and say something like "I'm not cute, I'm gonna rule the world someday!" which Yin always mentally facepalms at.

Yang has Wattpad. He always tries ruining Yin's innocence with it.

They absolutely love head pats! 

When in human form, Yin has blue eyes, Yang has brown eyes that can glow red.

Yin-Yang is the one who hangs out with Tissues the most out of all the hotel residents. Tissues likes this.

S m o l b e a n s. They're really short so they have to climb on top of stuff to reach things. Luckily Yang is good at climbing and Yin is pretty flexible, so together, they can do it easily. 

Yang loves climbing up the fridge. It gives him feelings of power. Yin thinks it's stupid, but he has decided to just go along with it.

Yin-Yang takes meditation lessons from Candle, so they get to learn more about themselves and each other. It has strengthened their bond heavily.

Back in season 2, when they had to sit in the Calm-Down-Corner, they'd draw on the walls of the CDC. Now in III, they just stack the pillows because why not?

Yang has made a DrFizz cult, which Yin heavily disliked.

I'll add more hc's when I think of em.