Older sister - Younger brother. Why?

[alberic]

What is it about the older sister - younger brother dynamic that makes it so popular? It is an overwhelmingly prevalent setup in stories both in the ENF and ENM genres, and it is a huge turn off, personally. Enough so that it is able to ruin stories for me that are otherwise well-written with a great premise.

I am genuinely trying to understand what makes it such a popular setup/fetish, because I just don't get it.

[Executionus]

It has two main roles depending on the type of story:

In ENM it places the girl character in a position of power over the boy (both physically and authoritatively) and works to add to the humiliation factor of the nudity because it's a male being dominated by a female semi-peer. Femdom is a very popular fetish even outside of ENM, and older sister younger brother is an easy setup for it.

In ENF it puts the girl character at a higher tier of maturity and development, causing extra humiliation when she's nude because she sees her brother (and his friends, if applicable) as being beneath her and unworthy of the view of her goods. It also allows for sex ed plots where the boys learn about the secrets of the female body by studying their reluctant "volunteer".

Of course the reverse is popular too, older brother younger sister, and there's plenty of examples of that across the board. Usually younger sister stories involve innocence play, dom/sub fun, or an extreme reversal of expected power dynamic.

[montyblanque]

I am genuinely trying to understand what makes it such a popular setup/fetish, because I just don't get it.

I can't speak for others, but IMO sibling incest doesn't give me the 'ick' because I never had sisters growing up. A part of my brain always views these stories with a level of 'disconnect' from reality that lets me enjoy the scenario as I feel "well it's not MY sister..." even if I'm reading a 1st-person perspective piece, they may as well be step-siblings.
In addition, having not grown up sharing a house with a girls, the idea of coexisting in close quarters during the height of sexual curiosity creates a fantasy in the vacuum of the mystery.

[alberic]

sibling incest doesn't give me the 'ick' because I never had sisters growing up. A part of my brain always views these stories with a level of 'disconnect' from reality that lets me enjoy the scenario
...
having not grown up sharing a house with a girls, the idea of coexisting in close quarters during the height of sexual curiosity creates a fantasy in the vacuum of the mystery.

That's a fair observation. I don't have kids, which likely allows me to enjoy father/daughter incest fantasies to the full, unencumbered by reality. If I was a father IRL, I would probably see things quite differently.

[montyblanque]

That's a fair observation. I don't have kids, which likely allows me to enjoy father/daughter incest fantasies to the full, unencumbered by reality. If I was a father IRL, I would probably see things quite differently.

Indeed, perhaps thats why father/daughter stories bother me? While I don't have a daughter myself, my friends have daughters, and being a sort of 'uncle' to them since they were born has given me a degree of parental perspective. (I'm also not a fan of 'minor+adult' narratives, but I'll admit that's just preference.)

[NickTwisp]

In a lot of families an older brother is looked at as a (sort of) semi-authority figure. So, if the younger siblings (especially sisters) see him naked, to me at least, that is even more embarrassing than the reverse scenario.

Especially if it's accidental, like sister walking into the bathroom while he's in the shower.

[superevil7]

Like others have said, it's the added layer of embarrassment of having a younger sibling in a more powerful position over the older one. I'm also not a fan of adults taking advantage, but I will do it the other way around if it fits into my story, for the same reason as above.