Personally, I don't see the difference between stepsibling stuff and blood relation, at least on a moral level. Like, if you find out you were adopted, does that suddenly make it fine to have feelings for your sibling? On a primal, genetic level it's the actual relation that makes those kind of things messed up but from a social aspect, with how people judge you, there's almost no difference. I've never really seen anyone who thinks that things happening between stepsiblings in real life is totally fine, but if they're related it's totally wrong.  So that's why I didn't specify, because I didn't think it matters. "Either it's all OK, or none of it's OK." Also, I tried to make it very clear via Reese's thoughts in chapter 1 (and 2) that he has no feelings towards his sister. That won't change, and she won't develop anything for him either. "Sexual things" will happen eventually (not actual sex), but it will be more about her controlling him than anything. Power, not love or lust. I don't have any plans for either of them to get turned on by any of the experiences.

So with that in mind, and with that being said, it's not important to the story that they're blood related and there's no mention in the story (or do I plan on there being) of Tracy specifically birthing Olivia and Reese with Stuart as the dad. The important part is the relationship dynamic that they share as people who grew up as a "family" together. If you want to imagine them as stepsiblings, I can assure you there won't be anything in the story that will break that head canon :)

Reese won't shrink any further, not as a slow size change at least - although the next versions will see him at around 3 feet, 1.5 feet, and 8 inches. I liked that idea because then I don't have to wonder like I do with other slow size change stories - oh, what if he shrunk just a bit earlier? Or just a bit later? I can see how the interactions would carry out over each size, you know? It'll be awhile before I get around to those iterations but they're definitely coming and I have plans for how they're going to be different and add new subplots, and not just changing up a few words. I think most instant size change stories either have the main character having been at that size their whole life, or they make themselves that height, or someone else does. So I like designing my story like this because neither Olivia or Reese wanted him to be small, but it's a relatively new experience for both of them. 

Whew quite the response haha! Thanks for your feedback and questions though!