When Thicker Than Water is pushed to its furthest extent, it leads to loyalty to one's entire species.
This generally requires at least one other intelligent species around, to prove a contrast from a general benevolence toward intelligent beings. They are compatible, just as people can support their families more strongly while behaving well toward non-related individuals — but Moral Myopia is also possible, which can cause Fantastic Racist or Transhuman Treachery. A Genghis Gambit may be used to cause unity.
And it does not keep members of that race from acting as a Dysfunctional Family outside of crisis. A united front may be seen only in times of crisis, facing down aliens or a natural disaster. Those who collaborate with alien invaders are often particularly hated for this reason.
May be a reason for Mandatory Motherhood. If a species is in danger, anyone who can have children and doesn't will be accused of lacking this.
Half-Human Hybrid — or half-whatever hybrid — may be regarded as treacherous on the parents' part and untrustworthy on the child's, because of it. Technically, all such hybrids should be sterile, since that's the definition of species but many works ignore that.
- In Watchmen, the plot was to feign an alien attack to draw this out of humanity.
- One issue of What If? has Magneto using his space station Avalon as a safe haven for the majority of the world's mutants. Despite his leadership, as the years go by various secessionist factions develop among them, one wanting to return to Earth and take it over with their combined power, and another wanting to leave the galaxy altogether and find a new planet to call home. Then one day the first baby is born on Avalon, and tests show it to be not Homo Superior but Homo Ultima - an omega mutant that will not only have complete control over its powers, but will be able to choose them. The mutants freak out, steal the baby from its parents and kill it. They then decide to put aside their differences - after all, mutants need to stand together, in case any more of those Homo Ultima show up. At the end of the story, of course, we see that Magneto falsified the test results to bring about this very outcome. He had to keep his people in line, even though in doing so he caused the death of an innocent baby and proved that the mutants are just as bigoted and hateful as the humans they escaped.
- In Chrysalis Visits The Hague, neither the ponies or changelings have a very good opinion of each other. To the former, the latter are unscrupulous monsters, while to the latter, the former are hypocrites and the true mindless drones. Also certain humans have become increasingly paranoid with the increasing Equine presence in their cities.
- In Children of Men no children have been born for more than 20 years. Whenever Kee's baby cries it sparks an instant and almost universal reaction of "must protect" or cessation of all hostilities among total strangers. Only one corrupt army officer tries to capture them for personal gain.
- In John Hemry's The Lost Fleet novel "Invicible", the spider-wolf aliens know that the Syndics and the Alliance were at war, and regard the fleet's charge to Midway as their "helping our brother-enemies against our not-brother-enemies", and as extremely impressive.
- In C. S. Lewis's The Last Battle, the dwarves' rallying cry is "Dwarves for the dwarves!" They don't want the Aslan side or the Tash side to win. During the battle they use their arrows to help whichever side is losing at that particular moment.
- From Starship Troopers: "Either we spread and wipe out the Bugs, or they spread and wipe us out - because both races are tough and smart and want the same real estate."
- Averted in Max Fraj's Labyrinths of Echo. Understandable since most humanoid species there are cross-fertile.
- In Sergey Luk'yanenko's "Key Dach" novels, as those take place in a modified Master of Orion universe.
- In V. Panov's Secret City, partially enforced by The Masquerade of the setting when dealing with respective Muggles, with notable differences among the magical nations and among the magical species making those up.
- In V. Zykov's Way Home: both examples (reptarkhs, reprokhorses, light elves, dark elves, high and common dragons) and counterexamples (humans, dwarves, goblins).
- In most works of V. Ivashchenko: united elves, fractioned humans and tribal orcs.
- In Andre Norton's Secret of the Lost Race, an alien race can interbreed with humanity — and in fact must to reproduce — and this is greeted with revulsion and accusations of disloyalty by many humans.
- In Poul Anderson's "A World Called Maanerek", Sonna thinks it a glorious thing to make all men brothers again. It is when she learns of the Dystopian nature of the Hegemony that she rejects it.
- In Poul Anderson's After Doomsday, the human ships seek each other out, both for more humans and in hopes of perpetuating the race.
- In Robert A. Heinlein's Have Spacesuit Will Travel, Kip and Peewee ask to return to Earth even if the judgment goes against it, though arrangements have been made to let them live out their natural lives.
- In Sarah A. Hoyt's Darkship Thieves, Thena's father complains about her lack of loyalty to her genetically engineered species. Given that species has been living by cloning its own members and then murdering them to transplant brains into them, she doesn't take it very seriously.
- In John Scalzi's Old Man's War novels, human conflicts are damped down in the name of unity in the face of the many aliens who want the same planets and resources as us, and are often far more dangerous than human forces. Later books reveal the human government is using species loyalty to maintain their power over humanity, and that the aliens are not all so hostile - in fact, we're one of the handful of rogue states that would rather stir up trouble than get in line for peaceful disbursement of habitable planets.
- In Poul Anderson's Sargasso of Lost Starships, Jansky appeals to Donovan on this ground — yes, they are from different planets, but they are all human. Unbeknownst to her — he knows they are going against aliens, and it invokes this.
- In The Mote in God's Eye, the existence of, and threat from, the Moties greatly helps unify mankind.
- In Warhammer 40,000, the official principle of the Imperium is xenophobic species loyalty. However, the human race has been split by the Horus Heresy, and there are those who willingly use xeno tech. Tau gue'vesa units (indoctrinated and/or voluntary human auxiliaries with Tau weapons) get the Hatred special rule from every Imperial unit.
- The Eldar, as well. The Dark Eldar consider the Craftworld Eldar to be weak, unworthy fools, and the Craftworlders consider the Dark Eldar to be absolute monsters (which is a pretty good assessment of them truthfully). However, this does not stop them from banding together to fight a mutual foe such as the Orks or the Imperium. Case in point: in the Allies rules, Dark Eldar and Craftworld Eldar count as "Battle Brothers", while the various human factions count as "Allies of Convenience".
- In Traveller the wolf-like Vargr fight each other like cats and dogs. However they always support each other when their species is even insulted. K'kree actually have species Xenophobia and not just loyalty, which is justified by the fact that most major races are predatory. Humans and Aslan by contrast have a mild species loyalty by comparison. Aslan are loyal to their clan and their code of honor and if their clan happens to be allied to a human empire that is OK by them. Humans in Traveller are as varied as in Real Life and a number of humans are allied with aliens against other humans.
- 1st Edition Dungeons & Dragons.
- The Player's Handbook had a Racial Preferences Table for humans and demihumans. Each race preferred dealing with other members of its race more than it did other races.
- The Dungeon Master's Guide had a Humanoid Racial Preferences Table for humanoid monsters (orcs, gnolls, goblins and so on). Each humanoid race also preferred dealing with other members of its race over other races, with a couple of exceptions. Hobgoblins and orcs only preferred to deal with others of the same or friendly families/tribes: they hated all members of rival families/tribes. Trolls only felt neutral toward toward other trolls and didn't prefer to deal with any other race.
- Inhuman - Myches have this as a borderline hat, after the whole species spending a long time in slavery.
- In Sinfest, Slick tries to appeal to their all being humans. He has to revise it slightly.
- In Freefall, Florence regards herself as a representative of her species, requiring her to act accordingly. She wrestles with the possibility of her actions causing her race to go extinct, but concludes she has to avert A Million Is a Statistic.
- Likewise, Sam, having stumbled upon a way to claim enormous amounts of robotic run time, prefers to commission the terraforming of a new planet for his species rather than use any of it for himself. He does this to draw them into the greater interstellar community by appealing to his species' greed, knowing full well that, without the bait the planet represents, the moment the Sqids find about Humanity's developments, they are going to be overwhelmed by paranoia and cowardice, bury themselves in their planet hoping nobody notices them, and never go out again.