Here is something I found at isitnormal.com under the heading "Is is normal for family to ignore what's obviously incest?"
My cousin is the only child of a single mother (my mom's sister). He still lives with her, even though he's 25 and has a job. He's never had a steady girlfriend.
Almost every time someone meets them, they will ask me if he's her boy-toy. They enter ballroom dancing competitions as partners. We call them Simply Red because they're both ginger, but I've overheard some of my mom's friends calling them Simply Bred.
It's obvious they don't have a normal mother/son relationship, but nobody in my family seems willing to admit it. Every time we mention them everyone looks awkwardly at each other, but nobody actually says anything.
Is my family trying to turn a blind eye to it out of shame, or do they not believe it? I hardly ever see them, so what they do doesn't bother me, but I worry that it upsets my mom.
I personally think it's not my problem, but do you think I need to say something to my mom about it.
Is It Normal?
It does sound to me like the family figures there is something there, but they find it easier for them to leave it unspoken. If they disapprove, what's the alternative, really? Turn the consenting adults into the police? They could do that, if they live where consanguineous sex is still criminalized. But to what end? To ruin the lives of consenting adults who aren't hurting anyone? This may not be the life any of them would want, or what you, the reader, might want, but as long as it is the life they want, they should be allowed to have it. It would be great if everyone could be supportive, but if they won't be, it is better just to leave it.
As far as the son never having a "steady girlfriend," it is entirely possible he's had many relationships and just not told his extended family. He could be continuing to have such relationships. These days, not everyone brings all of their love interests or sex partners to meet their (extended) families.
It's also entirely possible their relationship isn't sexual at all. The people commenting tore into the original poster for assuming it is.
Whether or not this pair has a sexual relationship, there are adults who are in sexual relationships, sometimes spousal ones, with their genetic or step parent. Contrary to bigoted prejudices, many of them are successful, attractive, educated people.