The Dead Dove Locker -- "I don't know what I expected."

[Mamorien]

https://www.scribblehub.com/read/1419041...r/1966125/
https://www.royalroad.com/fiction/120617...-education

Also, the author of Nude Planet: Kasha (see above) has posted to SOL the first three chapters of The Greenfield Family, which has no overt elements of the fantastic unless you count a conveniently common kink.

Unfaithful, inattentive parents in a failing marriage. Bickering siblings who can barely stand to be in the same room. A sister who jetted off to college and never calls. A long list of secrets and dark histories. These are the ingredients that make up the dysfunctional Greenfield family. But the oldest son's girlfriend has a plan to help repair this fractured family, by converting them to her own family's not-so-conventional lifestyle.

https://storiesonline.net/n/52852/the-greenfield-family

For those who don't want to wait that long, the whole story is available on ZBookStore now: https://zbookstore.com/s/3687/the-greenfield-family

The publisher's extended summary gives names to the family and to the nature of the kink:

Safe enough, mostly sane, definitely consensual.

The Greenfields are not what one would call the most closely knit family in the world. Mom Keiko and dad Rick are both cheating on each other and less than attentive to their five kids. Twin siblings Zander and Paula and little sister Bobbi are constantly at each other's throats. Big sister Lily disappeared off to college and never calls.

Only the oldest son Marcus seems to have it all together, which might have something to do with his free-spirited girlfriend Raven, who sees the dysfunction among the Greenfields and takes it upon herself to help fix this broken family.

And how does she plan to do that?

By concocting an elaborate plan to convert them to her own family's incestuous lifestyle.