My guess is that before all the porn it was extremely uncommon IRL, and still is nearly as uncommon after it.

But maybe some people literally wouldn’t have considered it until seeing the porn, so perhaps numbers are up slightly.

I always thought step sibling porn existed because people are turned on by actual sibling fucking but they can’t pretend to do that in porn.

I’m guessing it is not common at all. Porn does it because it’s a convenient way to explain how people got to the same room. Same with the girl next door, handyman, pizza delivery dude etc

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It’s probably a lot more common than young adults fucking their babysitter. They’re somehow old enough to enlist in the army, yet too young to be left home alone for an hour? Maybe both that and step-incest benefit from being commercially safer versions of fantasies that can proxy for less marketable ones.

Do some ppl want it? Maybe Are a lot of ppl doing it? No

It deffo exists. Incest exists in many levels but it’s not commonly reported. It varies from abuse to consensual. How “common” it is depends on the “level”. From brothers/sisters that have hit puberty around the same time (maybe 2 years of separation from each other’s age) have at some point at least had wet dreams involving each other and everything from there to the point of full-intercourse at least once. Parental incest is less common but the next level and secondary family members are the third level of common incest. If you look for it, a lot of reports say incest is growing in America but there aren’t any official numbers, so… who knows?

No, I think it’s the easiest way to hand wave any two random people fucking. Plus the easy taboo edge.

The trend only exists in silly titles of porn videos.