Like you, I am not into incest... though you'd probably never know it considering that so much of it is in the story; but in my defense, I knew that if I was to include it (which happens to be a major selling point in Adult Game currently), I wanted to do it where it was imbedded within the story and made sense for why it occurs.
To be honest, there's quite a few things in this game that I am really not into... heh, but I wanted to tell a story that exceeded people's expectations, raise some eyebrows and try to entertain the hell out of people... not sure I exactly succeeded in that, but it has been a new experience, that's for sure!!