You know, not that I'm endorsing, substantiating, or otherwise confirming anything of an endgame nature... but I don't see why some people think patreon rules would prevent a non-related male from dating and being intimate with two bio-sisters (happens all the time in these games, including ours). As long as said sisters aren't doing anything directly together, there should be no issues, even if they do it with the MC at the same time one riding his cock and the other his face. Just so long as they don't kiss and make it weird... /end sarcasm
Besides the argument that none of this is real or exploitation... It is still all semantics when it comes to that kind of incest anyway. I mean, what is really the difference if Jenna tasted Katie on the MC's cock? Or got it directly from the source as Katie cussed and moaned about "how her sister could have gotten that good at oral sex?" And then "Not to even think about tickling her brown eye!" Even if the [MC] insists Jenna get her ready for anal. Followed by ass to mouth if she keeps bitching...