I'm torn with the incest in the smut thing.
Obviously, it's bad in real life. We had a massive problem with a certain family near where I live. There were books and news reports about it when it was finally revealed to the world, like three/four generations who thought it was 'normal.' They were all homeschooled, never left their farms, like ever, other than to sell crops. It was tragic that they literally didn't even know any better.
In writing, it is like a taboo, a proverbial Apple of Eden. A temptation that you know you should never allow, but... what if it did? I can see the appeal of writing about such situations, and I have read plenty of taboo things like that. And there is no actual victim in writing, no deformed incest babies, nothing that hurts real people.
So, you do you, Author. Write about your MC's mommy taking care of his every need. Just make sure it is tagged as such LMAO.