not just in china, most asian countries call each other brother or sister if they are close or if they don't know them as sign of respect, though I think it's just wrong translation but there are words for family brother/sister and stranger brother/sister
Yes I know that it's not only in China but in this context the work/manhua is and I do get it that you can use it in a lot of ways but here it's they using as a endearment/title to someone that they could potentially have feelings for. And yeah most of the time it's translation, I got it(⌒▽⌒)
No, I'm pretty sure translation is right in the usage of sister/jiejie. In Asian countries we often call people older than us sister/brother as a sign of respect and just a title for them. But if they're so much older than us it's usually uncle/auntie. It's like how I can say brother to someone I just met/don't know. It can also be used in context to love or a crush because they are older than you, you can say sister. So yea it has a lot of uses
From Lads, cdramas and other form of media I thought if i didn't think about it I can get over this but after reading this I realized that I don't really fuck with it. I know it's normalize in china and good for you people that's in to that you do you. It's not for me. (●￣(ｴ)￣●)