Actually, if I may (aside the fact he is still on Patreon), the version I have from Zorlun himself, and he said repeatedly, is a bit different.
It is true that Patreon forbade any incest, including "step-something", but that created a major problem only for Marc.
For Katherine, maybe there could have been some scene were both appear like it happened already (Myriam "spying" on Katherine, or Katherine "spying" on Myriam, or talking while both naked), but Zorlun was very explicit that she was never meant to become a "Myriam 2".
In short and simplifying, Myriam lost her innocente long ago, though she can be still naïve, Katherine has the body already of a woman but still her innocence, even as she starts to explore sex, and her mother is trying to make sure that the only people she gets in contact with sexually are William and J, who are also protective of Katherine, although more experienced (if the player had William doing something with Myriam) and more experienced and "wild" (in the case of J).
About the orgies, those are Myriam's, not Katherine, it is has nothing to do with the game in itself, the game is not called "everybody's orgies", is called "(project) Myriam", if one plays in a certain way, it can become "Myriam orgies", but still "Myriam".
About the dog(s) (though almost only Cassius) and the horse, those are forbidden by Patreon as well, and are additions to the game from someone else, because Patreon explicitly indicated they can even come under a false "name" here, check, and if they see Zorlun has anything to do with that, close his account and cut his Patreon income without further notice.