(Sorry not sorry, maybe) but sister or it could be brother, it was not at all dub-con. Karlyle clearly consented when Ash said he won't be able to stop even if Karlyle cried and said to stop. Please re-read chapter 91 again to rid of any misunderstandings (✿◠‿◠)
It was perfect… until chapter 91+
It’s always always always dubious consent.
Sorry for venting, I’m just very tired of this trope…