Why does it say role play and customize when not long after it starts she is revealed to be your daughter? You might as well just point out that its father daughter incest if that's the story you are going for.
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Incest is strictly forbidden on Patreon. If any game has incestuous content, the developer is liable to be suspended or outright removed from the Patreon platform, which could cost the developer what little support they might have. A Petal Among Thorns is about a middle aged man that brings a friend to a vacation retreat. You can apply whatever title you like to your friend. It's completely up to you and I, the developer, would never impede your freedoms to make whatever choices you want. :-)