Nope. Incest is defined as having a close blood relation, even in USA (I assume, maybe wrongly, you are from there).
I already made an example for USA-based people without names, but to make it clearer, it is famous that Soon-Yi Previn became stepmother of her stepbrothers, by marrying her adoptive father Woody Allen, and they could do it, because she had no blood link to Woody Allen.
As far as I recall (but I may be wrong), Mia Farrow's lawyers wanted even to try the "incest" card to create legal trouble for Allen, but it did not work out, exactly because there was no blood link.
There are cases, and States in USA, where sexual activity is automatically illegal, even if consensual, if one of the two is legal guardian, specifically in case of certain age factors (one of the two being minor, and the other legal guardian/tutor of the minor, even if already above the age of consent), and I think (but here, I can be even more wrong, I am not very deep in "celebrity news"), they tried even that, but if one looks at the date when they got married, she was officialy 27 years old, so, way above that, and if I remember well, even when they they started their relation, she was already above the age to be legally independent.
I had an exchange with Zorlun in the past, and as you can see even from his past posts, although I would not use some of the words you used to define them, it is clear that Patreon simply said made a blank interdiction, which meant any reference to "son", "mother", etc. would hit the wall.
It is not a legal matter, it is a (Patreon) policy matter.