guys I have a theory that maybe they aren't related and he's just saying that because maybe Hyo-seo's father created haeil in a lab because he used to work for the company. And saw him/treated him as his own son. That's why Hyo-seo use to be close and hangout with Haeil all the time as children because his dad was studying Haeil's behavior for the company. And the older brother is just saying that to Hyo-seo's father to get under his skin cause he know haeil is dangerous and protective over Hyo-seo that probably why they stopped seeing each other so abruptly because his father was scared for his son's saftey...idk tho maybe it's a stupid theory honestly hoping it's not tho because I don't want it to be an incest relationship
Spoiler Warning (づ￣ ³￣)づ you've been warned
guys I have a theory that maybe they aren't related and he's just saying that because maybe Hyo-seo's father created haeil in a lab because he used to work for the company. And saw him/treated him as his own son. That's why Hyo-seo use to be close and hangout with Haeil all the time as children because his dad was studying Haeil's behavior for the company. And the older brother is just saying that to Hyo-seo's father to get under his skin cause he know haeil is dangerous and protective over Hyo-seo that probably why they stopped seeing each other so abruptly because his father was scared for his son's saftey...idk tho maybe it's a stupid theory honestly hoping it's not tho because I don't want it to be an incest relationship