Mistaken for incest

[NotUnperson]

A while back, I was at a potluck lunch, and was chatting with an older woman I’m good friends with (and yes, we ARE just friends). One person thought I was her son, and I just joked that I’m actually her nephew. We just laughed off the misunderstanding.

I say this tale due to it being a source of inspiration. We’ve got an older woman/younger man (or vice-versa, if that’s your thing) that are lovers, but it’s clear they do care about each other greatly.

At a public event, the same identity misunderstanding occurs. They just laugh it off.

Later that evening, in bed, they’re still giggling about it, when one of them wonders “what if…?” Cue the roleplay…

 

[DarkSollat]

TBH I don't think it would for as erotic fiction. I mean, we can have an actual incest, so why to limit to roleplay? On the other hand, I once wrote a story where the couple and their fwb were cosplaying in bed instead of writing a smutty fanfiction, so there's a market for anything really.

The better idea would be an exact opposite of that. We have Mom and Son or whatever relation you crave, and they are mistakely took for a couple. Then:
1. They just laugh it off.
2. They laugh it off, but something happens. Like Son hugging Mom from behind and she feels his huge cock through their clothes.
3. They use it to their advantage, like getting a couple discount or something. May involve some form of proving their love, like a quick kiss.
Either way, when they're at home, it gets to their heads and they fucking.

Yet another another idea build on what you proposed. So Man and Woman roleplay as Son and Mother, but later this gets them wonder what it would be with their real families. And then incest ensures.

 

[grey228]

OP probably wants a set-up like this short film from 2015

 

[AussieIronman]

The better idea would be an exact opposite of that. We have Mom and Son or whatever relation you crave, and they are mistakely took for a couple. Then:
1. They just laugh it off.
2. They laugh it off, but something happens. Like Son hugging Mom from behind and she feels his huge cock through their clothes.
3. They use it to their advantage, like getting a couple discount or something. May involve some form of proving their love, like a quick kiss.
Either way, when they're at home, it gets to their heads and they fucking.

This would work for a brother & sister incest. They live in different cities, but meet in another city for a marathon or triathlon event that they both compete in. They are both married but their spouses stay home as they are not into sport. They might even stay in twin-share accommodation to save money.

The night before the race they go for dinner then to a club. There is an informal dance off at a club, which they enter because they both love to dance and their spouses dont. It gets down to three couples. Then the slow music starts, so the dancing gets more intimate. The crowd starts chanting "kiss, kiss, kiss" so they kiss passionately and win the dance off. The rest writes itself.

 

[DarkSollat]

The crowd starts chanting "kiss, kiss, kiss" so they kiss passionately and win the dance off. The rest writes itself.

Their kiss may even be innocent. But then, at the hotel...

"It was crazy, wasn't it?"
"You mean our kiss? It was."
"Yep, our kiss. It was nice too, I must say."
"It was. Listen... Is it wrong that I kind if want to do it again?"
"Me too... So, are we doing it? It's just a kiss."
"Yep, just a kiss. Nothing big."

 

[Carnevil9]

.....3. They use it to their advantage, like getting a couple discount or something. May involve some form of proving their love, like a quick kiss.......

If they want to prove that they are a long-term couple, just have her correct everything he says.

"You've corrected every single thing I've said for twenty years!"
"Twenty-one years."

 

[Small_Island]

A while back, I was at a potluck lunch, and was chatting with an older woman I’m good friends with (and yes, we ARE just friends). One person thought I was her son, and I just joked that I’m actually her nephew. We just laughed off the misunderstanding.

I say this tale due to it being a source of inspiration. We’ve got an older woman/younger man (or vice-versa, if that’s your thing) that are lovers, but it’s clear they do care about each other greatly.

At a public event, the same identity misunderstanding occurs. They just laugh it off.

Later that evening, in bed, they’re still giggling about it, when one of them wonders “what if…?” Cue the roleplay…

I'm going to half agree with DarkSollat. Having the May-December lovers go back and role play an incestuous mother-son relationship later could allow you to write a hot scene, but since it's just pretend, I'm also not sure if it would score well with LIT's I/T audience.
But rather than flip it 180 degrees and have them be real mother-son, I'm wondering what we could do with your concept of mistaken mother-son.
Imagine that they go into the role play as you propose and really, really get off on it - surprising both with the intensity of their excitement. That could be part 1 as a stand alone story. But then, continue into a series where they talk about the strength of the role play.
SHE: is that because you'd really like to fuck your mom? (who is same age as SHE.)
HE: as much as you'd really like to fuck your son. (who is same age group as HE.)
Then, the next installments have them conniving together to seduce each other's parent/child into real incest. It evolves into threesomes centered on each of the MCs and then a foursome.

 

[Small_Island]

I'm going to half agree with DarkSollat. Having the May-December lovers go back and role play an incestuous mother-son relationship later could allow you to write a hot scene, but since it's just pretend, I'm also not sure if it would score well with LIT's I/T audience.
But rather than flip it 180 degrees and have them be real mother-son, I'm wondering what we could do with your concept of mistaken mother-son.
Imagine that they go into the role play as you propose and really, really get off on it - surprising both with the intensity of their excitement. That could be part 1 as a stand alone story. But then, continue into a series where they talk about the strength of the role play.
SHE: is that because you'd really like to fuck your mom? (who is same age as SHE.)
HE: as much as you'd really like to fuck your son. (who is same age group as HE.)
Then, the next installments have them conniving together to seduce each other's parent/child into real incest. It evolves into threesomes centered on each of the MCs and then a foursome.

Alternate thought just popped up for if you don't want to go down the real incest route.
They go back and role play as you originally suggest and do really get off on it as I suggest.
However, rather than turning it into the real thing with relatives, it goes into an E/V realm where they set up an OnlyFans site where they pretend to be a real mother-son couple and do their role-playing live for paying pervs. Bringing in the interactions with fans who really want to commit incest would open up a lot of ground for you to farm.

 

[DarkSollat]

Those are solid ideas, @Small_Island !