Ok: I made the game basically with a flag (incest true/false) which got set by the dialog at the start of the game.
A typical dialog in the game looks like this: "This is my [MOM] and I want to motorboat those melons!"
At runtime, I just replace [MOM] with either "mom" or "step mom" depending on your choice.
That was the old situation!
Now for the new situation: I removed the dialog.
No way, if it comes to that, I'd rather either make the whole text editable and "upload language packs" (which would of course also have the benifit of "fan tranlsations") or just move away from Patreon.