Responses
It was mistranslation
It was meant to be: she doesn't know who he is. As like that he's part of this rich dangerous family
That's why bro trying to have Teaha go on this trip, because he kinda figured out that Taeha keeping from Naesoo his background and going pretty far to hide it
He's planning to do smth with Naesoo while Taeha away

What did he mean by saying: does he not know who is she? Is she an illegitimate child of a rich house or smth #-.-)