Whats this ? someone smart that ahs actually done research instead of spouting the same tired trite that society has hammered into their skull ? colored me surprise...
The main issue with incest is the societal taboo of it, not the genetic defects... You need to inbred like fucking crazy to start producing mutants... I believe first generation incest children get a lousy 3% higher chance of birth defects compared to a regular baby... if the siblings of that union do it again it goes to 9%, than 27% , and five generations down you start producing kids with no immune systems, weird teeth, fragile bone structure etc...
Research has been done on the bones of the Egyptian Pharaohs and their bloodine (one of the most clear cases of incest in the ancient past) Tuten-khamen or whatever the most famous child pharoah was one of the most clear examples of incest gone wrong, and I believe he was 8th generation of a purely incestual line...dating back to Princess Nefertiti...
Also FCreations has already made it clear that its not about patreon, his game was always meant to be played as Step-siblings, Alice is not blood related to the MC... that said, the guy that said they only know each other for two weeks is wrong... when the game starts (unless my memory is fuzzy) it was stated they grew up together for a few years when they were kids and eventually got separated, he hadnt seen her in over a decade or so.