Responses
Well... one of the parties never saw the other as a brother. I don't know... there must be a limit where even if one person is the "active one" they are still victims of manipulation. It seems like the blondie, had a crush on him, and used the MCs feelings against him, as well as his guilt. I also think that there was an implication that many a times, they slept together because the MC was drunk.
Ick I forgot the main guy committed incest. Yk, the author didn't have to put that into the story but of course they did. Do they not realise how gross that is?