psycopath into incest, boy does the plot thickens
Well, not incest exactly. But pretty close. They are step-siblings and have known each other since they were 10 (so 6 years I believe?).
10 is bit of an iffy age to create that mental barrier, but I would say for most, even if it was their step-siblings they didn't care much for, just trying to think such things would feel very icky?
But let's be fair. He is a god damn psycopath. A psycho on the lower part of the spectrum since he can develop some form of love, but still.