Weird Genders and Sexes for Fantastical Races

One thing that has forever bugged me about science-fiction is how almost every single alien basically follows the same sex and gender dimorphism as humans: females are smaller, males are larger and rule everything, blah blah blah. If you're especially unlucky you get the trope where the guys are all monsters and the girls are all super hot. If you're double especially unlucky and you have the misfortune to be reading Ringworld you get the trope where the men run society and all the females are off-screen the whole book.

Anyway, here's some reproduction methods and gender roles for your wacky alien species. I've tried to take sexual roles from real-world organisms and try to extrapolate how that would work culturally. I've included multiple cultures per species, since obviously people have loads of different gender roles despite all having the same reproductive strategy.

1. Swamplings: Time-Based Protandry

Swamplings live in wetlands and kind of resemble frogs with bio-luminescent anglerfish lures and five eyes going all the way around their heads. They practice Protandry: they are born as males and remain males through adolescence and adulthood. Upon reaching a venerable age, they turn into females if un-mated, becoming more hardy but less physically capable. They reproduce via sexual reproduction, and the females lay eggs. 

a. Northern Swamplings: The Northern Swamplings are nomadic, travelling around the Great Blue Swamp. Their men are seen as expendable and used as warriors and hunters, while the women are responsible for taking care of the children and serving as rulers. Monogamous pairs are formed with one older female and one younger male; when the older female dies the younger male will change sex and eventually take on another mate. Homosexual behavior (but not "marriage") is considered normal for males, since there are always more men than women, but unacceptable for females.

b. Marsh Swamplings: The Marsh Swamplings live in reed huts, keeping fish as livestock. In their tribe, polyandry is common, with most women taking multiple males as husbands. Marsh Swamplings believe marriage is for life, so men who have been married are not allowed to marry again after becoming female. Because of this, first-born children will usually not marry until old age. Husbands are expected to do almost all of the child-rearing and farming together with their brother-husbands, while Wives mostly handle politics and make art. Homosexual marriages are legal only for older women, though some families will look down on it.

2. Ratfolk: Hermaphroditic

Ratfolk look like six-limbed rats with no eyes and long tentacles on their nose. All ratfolk are hermaphroditic, capable of both becoming pregnant and impregnating others.

a. Mountain Ratfolk: Mountain Ratfolk have a very traditional culture that emphasizes respect for one's parents. Their culture practices arranged marriages. It is traditional for the child from a higher-ranked family to be the one to get pregnant, since the traditional book of Rodentism claims that the child will have the soul of one of it's mother's ancestors. Ratfolk are interested in human gender norms as a cool exotic trend, and deliberately mimicking the dress-style matching one's current sex has become somewhat of a fad. 

b. Hill Ratfolk: Hill Ratfolk deeply value wisdom and learning. They believe in equal marriages, and take turns being the one to be the mom. Hill Ratfolk find the human concept of gender incredibly alien and do not understand it.

3. Elves: More than Two Sexes

Elves look like tall, ethereally attractive humans, with strange eye colors. While humans have only two sexes, elves have five: Up, Down, Strange, Charm, and Effervescent. Each sex is capable of mating with one of the other four. The sexes are distinguished by a complicated combination of eye and hair color. Elves don't naturally have external genitals but are easily capable of growing male or female genitalia compatible with humans at will, explaining where half-elves come from. Elves don't need to lay eggs or give birth, instead doing some weird bullshit magic thing that makes new babies grow out of flowers. Humans are terrible at telling elf gender, instead usually assuming they are men or women and using pronouns based on that. Elves can easily tell which human gender a human is, but use the same pronoun for all humans that they use for especially ugly animals and certain fungal infections. 

a. Valley-Elves: Valley-Elves have strict gender roles for all five genders. Laws on marriage is exceedingly complicated and makes little sense to anyone from other cultures- marriages are allowed between certain genders of elves but not others, and in some cases Valley-Elves may take multiple partners. All of this is the result of thousands of years of culture, tradition, and religion. For example, a Strange Elf with a Charm Wife may also take an Effervescent wife or a second Charm wife, but a Strange Elf with an Up wife may not take on any more lovers. Same-sex marriage is prohibited. However, Valley-Elves in the past have been granted the legal status to identify as a different gender than their birth sex, inheriting all the legal rights as such. 

b. Wood-Elves: Wood-Elves are largely gender-equal, though there are still expected gender roles and stereotypes. Same-sex marriage is legal.

4. Hobkins: Bidirectional Sex Changes

Hobkins, also called "Desert Goblins," are short humanoid creatures with scaly skin, large eyes, giant dog-like ears, and long, prehensile tongues. Hobkin determine sex based on characteristics, rather than the other way around. In any group of Hobkin, the largest 50% will switch to being Female, growing beautiful red and green scales around their necks. The smaller 50% will spontaneously switch to being Male, growing camouflaged skin-colors . "Large" seems to be somewhat cultural but is a combination of height, mass, and strength. Hobkin who leave their tribes to live amongst other folk often find themselves much smaller than everyone else, resulting in the majority of Hobkin wandering the world being male. This has led to the perception among the uneducated that Hobkin are entirely male

a. Desert-Hobkin: The most common type of Hobkin. As you might expect, Desert Hobkin have a female-dominated society; males are not allowed to own property or hold political power, and their only role is to marry a woman. If one of the couple switches sexes, the marriage is annuled, and the individuals are allowed to re-marry, but otherwise divorce is outlawed. The dominant religion, Jershonism, even teaches that a male's afterlife status is entirely determined by his wife's position in the church.

b. Rock-Hobkin: Rock-Hobkin live in caves underground, and make their money off digging for gems. They don't have a concept of marriage or of inheritance; mating is something to be done casually, and all resulting children are raised communally. 

5. Ornix: Facultative Parthenogenesis

Ornix are diminutive Skeksis-looking birds with three legs and a pair of wings, who have opposable talons for holding tools. Ornix have two sexes, female and male, which are determined by the environmental temperature rather than by chromosomes. Ornix are capable of sexual reproduction, but female Ornix are also capable of producing eggs on their own through asexual reproduction. In order to do this, female ornix will engage in mating behavior with other females in order to stimulate ovulation. Some humans see this as a "virgin birth" and believe that the Ornix are thus holy, and will seek them out for religious wisdom. 

a. Mountain Ornix: Mountain Ornix live on the tops of mountains. They have small villages that are entirely female, and the females of a tribe raise all the children communally and grow crops for food. Male Mountain Ornix are expected to leave their home when they become adults at age 27, after which they become nomads, hunting for their own food in the wild and travelling from village to village and mating with the females there. Ornix women will often form lesbian "couples", though their society has no concept of marriage or sexual pairings as different from close friendships.

b. Jungle Ornix: Jungle Ornix live in the canopy of jungles, and mostly subsist on prey they can hunt from the jungle undergrowth. They have strictly independent family units consisting of a mated male-female or female-female pair and their children, who rarely interact with others.