You sound like a very strong woman.
From what I've seen on sites such as Literotica, the incest stories seem to be very popular and highly rated (here's the
favorites page). I don't understand it any more than you do, it squicks me out.
Also, to take me as an example, I happen to enjoy bi-porn. However, I don't desire having sex with other men.
None of this is meant to say that you shouldn't be worried.