Well, that is a good question indeed. Honestly, Zorlun was sketchy on details, but I think it is not because he want to the suspense, but because he is himself not sure yet.
Edit: just saw his post about this, replying to you - as you see, he is indicating himself that in his mind it was always possible, but that it is not planned, which means, he has not yet thought about how could be done without risking trouble with Patreon.
I clearly said that like for the content with Marc, if there is any character with whom I can make the incest become visible, I will do so - but I cannot create pictures (that requires getting scenes and/or subscenes from which to extract the character, and/or character presets, even if I had already the assets in my vast library), and I don't touch the flow (which would be required to insert the pictures anyway), those are both areas reserved for Zorlun, so it will be difficult to touch it through the incest patch.
The only way to do so, in the actual situation, would be if instead of being her father and brother, they were "someone she sees as a father" and "someone she sees as a brother", but that is already out of the question, it was explicitly indicated she would visit her father and her brother.