This is why I don't like love triangles (well I can say it's all starting to go in that direction). Seowoo started it, yes, to ask for his brother's help but now that he's growing some courage after his solo encounters with Ohn and wanted to act on his own, this twin of his who knew all along what he got through is being a huge prick towards his brother.
If he really has feelings with Ohn, then be man enough and act as Jaewoo and not hide behind your brother's name. He's acting like a manipulator here. He's now using his twin's name to get Ohn's affection. If it's not for Seowoo asking for this favor, never in your life you'll notice Ohn. And that is a fact.
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Spoiler!
Alright so in the recent raws, Ohn started to notice about Seowoo's mole on the cheek. This happened twice already, previously when he's drunk.