Yeah but the creator can't use patreon money to finance an incest project, theorically you can link to your page, twitter... however the incest, rape... content if it's linked with you then you will get banned.
Another thing is that the "complete version" appears on the internet with rape, incest... however the creator isn't linked directly, like posting on a forum under another name and never admitting that it's his work.
i dont think they can ban you for doing porn or incestgames or whatever if your patreon is for something else
People Who Can't Use Patreon: After creating a Patreon page, any creator caught in the act or convicted of making credible violent threats, committing violent crimes, child abuse, malicious doxing, coordinating nonviolent harm (such as fraud, money laundering and gambling), or encouraging others to do any of these activities, may be banned from using Patreon.
this is the only section in the community guidelines i found that references offsite stuff that isnt terrorism or hategroups and it doesnt prohibit porn production and whatnot. everything in the terms of use seems to be about the law aswell, also stuff like blocking usernames and data mining but not really relevant here
So he could make his patreon for producing adult artwork of his OCs and just do summertimesaga as a "side project" (keys for the filehost go to ppl who pledge for art via mail, he post like one pice of art a month on patreon, rest goes thru his site )
and/or he could maybe just put a disclaimer up ( that none of his caracters are bloodrelated and eric and the main character are adopted) and rewrite the beginning. the maincharacter calling other caracters "aunt" "sister" "dad" or whatever shouldn't be a problem then, they are to be seen as actors and in context.
this seems to have worked for atleast one other creators who had to remove beastiality from their game because patreon afaik (atleast it works atm who knows whats coming)
Edit: added some clarifications
