In order for this to be Oedipal, you'd need a prophesy that any party was fighting / fearing against. MC isn't, we weren't told of an Jocasta (that doesn't exist) fearing it, we weren't told of an Oedipus (that doesn't exist). How is the MC going to accidentally fulfill a prophesy that was never made?
The MC got his cum powers from somewhere, the cult makes the most narrative sense, not sure where you are going to get that power elsewhere.
MC grew up in Arenfeld... You are reaching...
When Emily finds the MC and Mira making out, she freaks out at the incest, and the player gets a quest demanding the MC reads his step dads notes, because the fear is that Mira and the MC are related.
You break in to your house, and find the note, you aren't related.
To then SURPRISE, I the writer Chyos was lying, they are related would just be ridiculous.