@TheGodEmperor The reason incest would cause problems is if their family had any bad recessive genes inbreeding would vastly increases the chances of offspring inheriting those recessive genes from both parents who share similar dna and ending up with bad recessive traits that would otherwise not have occurred if you bred outside of the family. Or just google incest/homozygosity or something i'm just a student im dum.
This alternate world probably doesn't have any terrible recessive traits lingering in families if the village was inbreeding for multiple generations without issue so there is no real downside to incest in this world besides the leftover social taboo from our world which only exists because we do have terrible recessive traits lingering in our dna.
MC running away from a problem instead of taking the time/effort to attempt to talk things out is immature for somebody who has lived through adolescence twice. Ghosting on people is fine if you don't care about them but leaving his family as a first course of action is wild.