Did no one think it was weird that when Cha Do Hyun,  and Oh Ri Jin found out that she was the girl in the basement that they never really addressed whether they knew for certain if they were actually half siblings or not? They showed us in a flashback episodes later but they left that open for too long I think.... 

AND then, ep 19 Oh Ri On as good as says he thought about what if she had never been taken from the basement, and if they had met later would she see him as a 'man'??  And then he says thats when he decided to be the best brother he can be and asked cha do hyun to protect her..... I mean..... What??? Why was that weirdness brought into it lol