No need to feel bad about enjoying the incest content! It's just a game, it's fantasy.
If anything it always annoys me a bit that it has to be the stepsiblings trope. Just make them siblings, who cares if it's a work of fiction? Does it actually turn people off if they're biological siblings, even for a fantasy? I thought the taboo nature of it was kind of the point.
Ahem, sorry, went on a bit of a tangential rant there.