No, they’re not blood siblings. They are both orphans and they were both at the orphanage (damrock or something). And spoiler:
Chulsoo actually liked Dajeong’s sister but it seems now that he cares about Dajeong more
Omg whaaat, Chulsoo liked her sister? Even in the past it seemed like he cared more about Dajeong, is it confirmed?
Yeah. He liked Dajeong’s sister because she was the first one who greeted him at damrock and he thought she was mature. He cried when he found out that she was alive. But he tries to convince Dajeong not to look for her since her sister didn’t want to recognize them. Afterwards, he tells her that his priority is Dajeong, but Dajeong responds that her sister is her number one priority and is before Chulsoo.
That’s sad :( thank you
Are Chulsoo and Dajeong really sibling? I kinda ship them, Chulsoo seems to deeply care for her