Yeon-ah and the dad being lowkey rude to woo-yeol is understandable. It's like a dad having a daughter and a brother who have a little sister. Seong-ah who had recently reunited with them after idk how many years suddenly dropped a bomb that he and woo-yeol are gonna get married. They don't know woo-yeol as a person + he indeed look like a thug compared to seong-ah who looks easy to manipulate. They're just worried for seong-ah but they means well ( specially the dad), dad even offers a room for woo-yeol when see saw woo-yeol super duper tired. About yeon-ah, well we can't do anything about that, it's a normal reaction if you and your siblings partner are not that close, and again they only recently met the guys.
This is one of my fav so I keep on rereading this. And when I reread the part where seong ah's family found him, I don't like how his family treat wooyeol. I mean I understand where their reactions came from but it kinda pissed me off. I'm having mix feelings because I understand that they are a bit over protecting considering they've been looking for seong ah for a long time but wooyeol basically saved him, so can't they treated him a bit kindly. I understand them but I don't know. For me wooyeol is one of the kindness character here except being a playboy