Here's a bit of what I had in mind for the background of the story. I know it's confusing and stupid sounding when you think about the situation, but I had the idea that Aavedia conducting under the same supervision of higher beings known as the ancient spirits mentioned previously. Aavedia has actually had contact with these beings and as a result has had her future fixed to a higher purpose than what she's capable of changing regardless of her actions. In short, her ongoing line serves greater purpose to these ancients, yet her continued line, her offspring in this case, cannot be born of the tainted, supernatural. They must be born from beings of will and borderline god-like qualities shown within the eye of the soul which shows in Guts who presents these qualities beyond his physical prowess. He's the only character used from the main story when I was writing her story out, so I thought others might enjoy it, but I refuse to post Aavedia's story since I already know that no one would care enough to read it (Plus it's borderline ninety pages and uninteresting to someone who doesn't take pride in my character like myself).
If you still don't understand, the just of it is that Aavedia needed to be pregnant by someone of qualifying soul apart from herself. Guts fit the description, so they were put into a situation where they felt as if they had no choice but to partake in the action of recreation or sex.