I think people are confused, so in the drama they both think they are sibling. Howeve, as an audience we know for sure they are not because they’re the main leads that love each other so they can’t be.
I’m not sure but when I was watching the whole time they think they’re sibling. That’s why zbb was holding his feelings back because he can’t love his sister. Buqi will find out in ep 19 and zbb will find out in ep20. That’s when they will clearly say “oh we are not sibling”
Omg I had to go back to watch the trailer and ahhh I can’t wait. Never felt so excited ever for a drama like this. Zbb and Ariel are so cute and the their chemistry is top notch! I think this drama pass every drama for me now.