This refers to Paypal, the service that Patreon uses to process transactions(and the people thanks to whom they get their money), not being fine with certain fetish content, incest being one of them. So if Patreon wanted to continue working with them, it needed to put a stop to all such content being hosted on the site.
Patreon went after all the devs that had loli, shota, bestiality, rape and incest in their games(quite selectively in some cases...) and put their pages on hold until they removed the offensive content. Some games had to redo art assets to age their characters, some had to remove content and offer it on different sites.
Most of the games with incest in them simply put a "What is your relationship to this character?" screen in the beginning of the game or just replaced all the occurrences of "mom" with "landlady". So this is why every second game on Patreon has either a landlady, roommate, distant cousin or a step-sister in it.
Thanks for coming to my history lesson.