I intentionally used the word "aversion" as it does create a certain uneasiness that almost makes me want to look away. It also boosts the taboo so in the end is a net positive.
Most initial scenes between the siblings when they are discussing their emotions about their feelings for each other, "we should" vs "we shouldn't", "it's bad" vs "it's alright don't worry". Mom having reservations in the beginning and her moral conflict is also a good example.
It's a fake story that contains incest so we know the end goal after all. Still if people play allowing themselves to get into the narrative I believe they'll experience a more "organic" progression where the dynamics change and evolve, ultimately leading to incest. In opposition to other stories where it's like "Oh I live with my
mom landlady and
sister roommate and suddenly, after giving them some compliments, they started sucking my dick :0"
P.S. I think the best example of this is
Light of my life where there's a story where it happens that certain conditions lead to the incestuous relationship between the main cast. Of course I also understand not every story has to be extremely nuanced. Some times you just want some easy smut and that's it.