Sedoretu

Sedoretu is a fictional polyamorous marriage system created by Ursula K. Le Guin in the science fiction story "A Fisherman of the Inland Sea". 
In the story's universe, society is divided into two halves referred to as moieties, with individuals belonging to either the morning or evening moiety. A basic sedoretu is made up of four individuals; two men and two women, with one man and woman belonging to each of the moiety. Each individual in a sedoretu is expected to have two romantic/sexual relationships: one homosexual and one heterosexual, each with the members of the opposite moiety. Same-moiety romantic/sexual relationships are culturally taboo.
In fandom, sedoretu is a trope that is used in fanworks, with the trope's popularity increasing after Dreamwidth user melannen created a meta post outlining various fictional romance and marriage systems that she enjoys.
==Definition==
This trope involves any fanwork where a relationship exists based on the following rules:
==Additional Rules & Terminology==
One's parents are mother and father. The other couple in the sedoretu are one's Othermother and Otherfather. The "baby word" for othermother is "ombu".
People can attach themselves to a sibling's marriage as aunts/uncles, which permits them to have culturally-permissable sex with the members of the marriage of the opposite moiety. The children of these relationships are considered "cousins" to the children of the marriage.
As a sedoretu is 4 people, it can expand to 8 places, with each of the people in the marriage bringing in a sibling(s) as aunts or uncles.
Children of the same pair in a marriage are considered "siblings" to each other, and are "germanes" to the children of the other marriage. Children of an aunt/uncle is considered a cousin to the other children.
Brothers, sisters, and "first cousins" (which appears from context in the text to refer to children of the same mother by different fathers) may not marry each other, as they all share a moiety.
There are regional differences in marriage customs pertaining to germanes. In some regions, germanes may marriage, and in other regions, that is considered an unacceptable marriage. Fisherman of the inland sea, page 165
==Alternatives to sedoretu relationships within the sedoretu canon==
Pairings/couples are referred to as "foreign marriages"Fisherman of the inland sea page 167 or as "couple marriages"Fisherman of the inland sea page 184.
At the Centers are "untraditional" relationships, which includes same-moiety relationships.
==Rise In Popularity==
The first major fanwork to use the idea of a sedoretu is An Ever-Fixed Mark in the Merlin fandom, written in 2009.
melannen also wrote a popular piece of meta outlining various types of plural marriage, including sedoretu. She comments:
This then inspired more meta and comment fic.Can't have one without the other Accessed 12 April 2011.
==Notable Works==
*An Ever-Fixed Mark by imperfectcircle
*Buffy of the Ki'O by sapote 
*Doctor Who comment fic by recessional
*Tony Stark is Not Getting Married (Today) by Circ_Bamboo (Avengers (Marvel))
*Just As Complicated As It Sounds by Mific (Stargate Atlantis)
*Four by Four by Elizabeth Culmer (edenfalling) (Homestuck)
*the path of gold and the world of men by Mertiya (Legend of the Galactic Heroes)
==Archives & Fannish Links==
* Sedoretu tag on AO3
* Morning Evening Day Night: A Sedoretu Fanworks Collection on AO3
* Sedoretu Fic Fest, including lots and lots of unused prompts
* Sedoretu Exchange (DW), a recurring fanwork exchange. AO3 Collection here.
* 40 Prompts For the Sedoretu (DW), a prompt and discussion comm for Sedoretu relationships. 
==References==
Category:RelationshipsCategory:Poly Fandom