melannen | The Importance of Siblings

The Importance of Siblings

So, as part of Hugos, I have read a lot more different original-worlds in a very short time than I have for awhile, so here is a worldbuilding rant aimed at Most Of The People Who Wrote Secondary-World Stories I Read:

If you are writing a world with a high death rate among young people - whether it's due to disease, war, accidents, space vampires, cage-fighting, spectacularly failing the magical initiation, your paper-and-balsa-wood wings failing at a terrible moment, being dragged away by Mysterious Masked Figures, whatever - your characters should not all be only children.

Even in a world with a low death rate among the young, you need a birthrate of slightly-more-than-2-per-uterus-having-person for a stable population of humans. With a high death rate, you need a birthrate substantially higher than 2-per. (Also, dear stories I read for the Hugos, if your base family unit is, say, triads of women, your average family size does in fact need to be six kids. If it's two men and one women, then a, what are you doing to all your girlchildren to get that gender ratio, and b, your average family size should be at minimum three kids. Or possibly two boys, a girl, and a baby girl you exposed at birth.)

If you're picking off a significant number of your young people before they breed, and none of them have siblings to carry on the line, your society is not going to last very long. With a high-death-rate society, two kids should be a small family. And they should have a lot of first cousins. A lot of them will be dead at a young age, but hey, you're the one who decided to build a high-mortality society.

(You also need your characters to have lots of siblings and cousins if your society is actively expanding into new land; if your society has a lot of outward migration; or if rampant population growth is a plot point of your story. Also, if a lot of your people of childbearing biology don't ever have children, the ones who do have kids need to have more kids to cover for the childless ones, so people will still have siblings even if they don't have kids.)

You can get away with fewer siblings if your culture is getting a lot of inward migration - if it's a city that's growing due to migration from the countryside, for example; or if it's an elite group of warrior-mages who bring in talented people from the outside population. But in that case, your society needs to show evidence that it's structured to take in a lot of people raised outside its culture, and your people from the outside population need to have siblings, since their culture is supporting both their own population growth and the elite group's.

Other than that, if all your characters are only children of only children, a rapidly shrinking population had better be a plot point.

(obviously if you go all-out to, idk, growing your characters in vats from gene-banks, or if they are left on doorsteps by storks, or if you have 0 mortality, all of this will apply very differently, but it'll still apply somehow.)

I get the reasons why authors write so many characters from small families. Most people getting published in English these days are from societies where small families are the norm, and especially in YA, are writing for an audience who are presumed to be from smaller families. (Although this is less true than you might think: a lot of modern low-birth-rate populations are doing the 'a lot of women don't have kids, the ones who do have large families' thing instead of 'everyone's an only child'.)

And it also greatly simplifies your storytelling not to have all those extraneous relations hanging around. And having your main character being the Last of Their Line is built-in Drama. So make your main character in a high-mortality society an only child with no cousins if you must. But they had better be an exceptional case, and your secondary characters better have siblings and cousins and aunts and uncles. And there had better be in-story justifications for why they are an exception.

And 'one of their parents died or disappeared when they were a baby' is not a good enough justification; in a high-mortality society there will be strong incentives for a single parent of reproductive age to remarry and give them half-siblings.

Bujold's Barrayar is a good example of how to do this well: Barrayar, at the time of Miles' birth, is a fairly high-mortality society between war and poor health care, and it's also actively settling a new continent and about to colonize a new planet and expanding militarily, and yet her three main characters in that generation, Miles, Ivan, and Gregor, are all only children with no first cousins. But there are story-relevant reasons for this: Ivan and Miles' fathers did have siblings, but they were all dead before marriage; Miles' parents want more kids and are under family pressure to have more, but know it would screw things up for Miles and Gregor if they did, so they resist the pressure; Gregor's mom actually was going to remarry and have more kids but got murdered first; Ivan's mother is under social pressure to remarry but resists it and is considered exceptional. Plus, Ivan's mother and Miles' mother do both start new relationships at an age when they could still have kids, though I haven't read the newest book so don't spoil me on whether they have yet in canon. And Miles actually does have maternal cousins, they just aren't a major part of his life for political reasons. And pretty much all of the other Barrayaran characters whose families we know about do have multiple siblings, and people constantly remark on the fact that it's weird that Miles and Ivan and Gregor don't. So Bujold gets away with it.

Bad example: Naruto. Okay I'm only about 1/4 of the way in, so maybe it gets better as Kishimoto expands the world, but so far we have a society where most people assume they will be violently dead by age thirty, and where there's a cultural emphasis on large lineal clans carrying forward certain bloodlines, and yet nearly all the main characters are only children, and the ones who aren't have only a single sibling. There is only one family so far with as many as three siblings (and the third sibling is treated as an unusual extra), and nobody has more than one aunt or uncle, either. And most of the characters who are in their twenties have no kids. Main character Naruto gets away with having no siblings because his parents both died the day he was born. But the fact that he has no aunts, uncles, or first cousins, and nobody finds this unusual, and the fact that nearly everyone he knows, even the ones who are supposed to part of large powerful sprawling clans, have at most one sibling and generally none, is bothering me more and more the longer I read.

So, conclusion: If you are killing a lot of characters, make sure most of them have siblings, and at least some of them have lots of siblings. You can have most of the siblings be dead or in another country if you need them out of the way, but they should at least exist.

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(If you change the rule that everybody dies exactly once, the 1:1 ratio changes, but what happens to population dynamics when you mess with mortality existing AT ALL is a whole nother rant. And something people screw up even more.)

Can I just step in to say, I've been fiddling with the math for this for quite a while and it is so fucking frustrating? I hope you do decide to post about that, because it's been giving me fits. The closest model I've got is a population pyramid with a loooooong tail, and it ends up mattering immensely how old the population is (it's hard to get an equilibrium when death is rare and optional), and it just all gets very complicated. On the one hand, if death in battle or childbirth or plague is too common, it makes it very, very hard to get enough children to replace all the young adults who, after all, are exactly as likely to die as are any other group, and yet if it's too uncommon, the population grows out of control.

(And it's hard to wrap my brain around what a family unit even looks like in that kind of society. Can you ask your eighth-great grandchild to babysit your youngest for you? I have no idea. There's no real-world precedent there, I guess.)

So yeah, I don't know if you know any more about that than I do, but it certainly is complicated.

(Also, thank you for this post!)

I may do a separate rant on that eventually (it will probably have a lot of talking about Tolkien's elves in it, because they do weird stuff with death rate...)

This is actually sort of an issue in modern population dynamics: there are countries with a sustained birthrate below 2 which still have a growing population, because people are just living a lot longer. In the long run the 2-per birthrate will still lead to a stable population, but in the short term it starts looking like a deathrate-less-than-1 society because the deaths are lagging well behind the births. If the lifespan hits a max limit, it will catch up with itself and stabilize, but it will be a stable population with a lot more adults in it at any given time than when the birthrate first drops. If the lifespan never hits a max, well, then you're on the way to your deaths-less-than-1 model.

In terms of fantasy versions of this: it really depends, in the details, on just how immortal your people are (are they actually unkillable, or do they die of stabbing a lot?), and you kind of have to shift yourself out of thinking in the paradigm of "generations" at all. And it also depends on fertility - if your people are fertile from 15-45 and are post-menopausal for millennia after, it'll look very different than if everyone's fertile forever, or if it takes people five thousand years to hit maturity. (I have read all three of those, done variably well...)

In the abstract I would probably shift to looking at it horizontally rather than vertically - that is, instead of thinking about how many kids a person has to have over a lifetime, since "lifetime" has became a much wobblier concept, you can just say that for a stable population, you need the same number of people born each year as die each year.

This shifts from the births-per-woman birthrate stat to "rate of natural increase", which is basically crude birthrate minus crude deathrate, which you want to be 0 for a stable population, and higher than 0 for population growth. So if 1% of the population dies in a year, you need 1% of the population to have a kid that year (and it doesn't really matter which 1% that is.) In a society with no deaths by old age or disease, you are probably going to have much less than 1% - in the US right now, death by accident/homicide/suicide is ~ 60/100,000, so if we were otherwise immortal, we would need 6 kids born per 10,000 people every year. (The current rate in the US is about 130 births/deaths per 10,000. So, in death-by-violence-only-world we would need 1/20 of the births we currently have.)

Converting from that to a full demographic profile and family size estimate depends on the length and timing of your fertility period, social customs, etc. and is left as an exercise to the reader. :P

What the society will look like is a much harder question. I can tell you when I have seen a book that does it wrong (hint: not exactly like modern American nuclear families, also no undying elves complaining about how their race is dying out because they only have a kid a century each) but there's a lot of possibilities, yeah.

(Right now I am confusing myself trying to figure out a society with a death rate *greater* than 1 death per person, and what that would even *mean*.)

Edited 2016-04-07 23:22 (UTC)

Ooooooooh! This is really, really interesting! And helpful. Especially the suggestion to abandon the idea of generations. Though age cohorts probably still make sense. (But then again... it probably does matter if your parents remember events from four thousand years ago, versus if your great-grandparents can only tell you about the last century.)

hint: not exactly like modern American nuclear families,

Why's that?

also no undying elves complaining about how their race is dying out because they only have a kid a century each

...At the very least, not without an ongoing pandemic or Thor trying to end you. Or they could be very, very warlike...

(Or fertility could be declining and they're extrapolating trends that won't even begin to affect them for another few thousands of years...)

Well, I mean, I suppose you could manage one with nuclear families if you really wanted to, but you'd have to work at it. Short version: right now, people who have kids spend something like half their lives either as kids living with their parents, or raising their own kids, so it makes *some* sense that "parents with kids" is our basic societal unit (although even then, 20th nuclear families are the exception, not the rule.) But if you reduce the number of kids at any given time by 1/20 at the same time you greatly increase the lifespan, average people are going to be spending a tiny, tiny fraction of their lives in those setups, and it will be an rare and fleeting life stage rather than the standard.

I've seen way too many stories where people supposedly live thousands of years, and the population is fairly stable, and yet the majority of adults are still raising young kids.

Fun fact: I once mathed out how long a lifespan I would need to expect before I'd be willing to spend 18 years of it raising a child. It came out to 14,040 years.

(This is assuming that women in my family can generally expect to live to be 90, and I would be willing to spend six weeks at childrearing, tops. Though if you assume longer lifespan = longer maturation period, that throws the math off.)

That sounds like an excellent goal to aspire to really.

tbh I would absolutely raise a child if it would get me that lifespan, or even a reasonable shot at it. If the kid could also expect that sort of longevity, they'd have time for a lot of therapy.

Ah, gotcha. My mental concept of "nuclear family" stretches to include "two people who might have kids someday" and "a couple and their thirty-year-old never-moved-out child" but by the stricter definition where the kids have to a. exist and b. be young, you're right. Though there could be nuclear families constantly breeding, so that for them it's most of their lives, but large swathes of the population *not* doing that.

I've seen way too many stories where people supposedly live thousands of years, and the population is fairly stable, and yet the majority of adults are still raising young kids.

PLAGUE! FAMINE! VIOLENCE!

...or maybe just breeding season that comes around once every five hundred years, so everyone has kids all at the same time. But also PLAGUE, FAMINE and VIOLENCE, because how else do you come up with a plot, right?

(Or an unstable, frantically-growing population, preparing its armies for the return of the Dark Lord while an ever-shrinking fraction of the population actually has firsthand experience of the First War, and... no, do not need more plotbunnies and I'm sure it's been done before.)

...Personally, though I have no principled reason for this, when I write long-term immortal committed relationships, I have in mind a model that's less about togetherness and more about... possibility. Like, you may live together this year, but you may spend a year *not* together, and where for humans "sweetie, I don't want to see you for a decade, I'll be off having adventures, call me iff it's an emergency otherwise I'll see you later" would be pretty much tantamount to breaking up or at least a sign of a relationship on the rocks, if you have eternity... why not take a break, even from someone you love? I know that's far afield of the topic, but since it's sort of about family structures: family as something you return to, rather than something that's always there, is an idea I like for immortal characters.

Ah, yeah, if you use a broader concept it works better.

But even then, I feel like, if kids are *that rare*, there's a reasonable chance that the basic childrearing structure would not necessarily be "a couple"? You will have a lot more adults per kid, and as ellen_fremedon is mentioning upthread, helping with childrearing becomes less of a sacrifice. And you also probably won't have the same concept of inheritance, and family relationships will mean something different when you can have a sibling a thousand years older and a great-great-great-great aunt your own age. So my favorite headcanon is that kids will be passed around and treasured among a much larger pool of adults of varying relationships to each other.

But you could go in a lot of directions! Just if you happen to go in a direction that is exactly like current American culture you really really really need to show your work.

Every >1 death rate scenario I can think of either reduces to the very long life-spans version (everyone is Jack Harkness; Time Lords) or partial-reproduction-by-fission (Homestuck AU).

Or you do something like, after first death you become a ghost or a ghost-in-the-machine, but when the stage between first and second death has so many different physical properties from the earlier stage, i feel like you could go pretty much anywhere in terms of social structure in that scenario.

Yeah, like, most cases I can think of, you either go "well, that death didn't count so they came right back" or it involves a new version being "born" as well (or both, or more-or-less that) so deaths-wise the math still comes out to 1 or less. Even with multiple stages, it's more like a butterfly, and the first death can just sort of get cancelled out of the math.

I think you have to go sort of metaphysical/psychedelic to make it work, like, idk, maybe a reincarnation scenario where all new babies are reincarnation of dead people, but there's a way to "twice-kill" someone so you also kill all their future incarnations? But even then you can reduce that back down to something with a death rate of 1 or less if you only count the twice-deaths and the new-births. Something weird with time travel that gets even weirder than homestuck? I may not be capable of thinking metaphysically enough. (I bet *someone* tried to right a deathrate-more-than-1 in the 60s though.)

Or, what if you do something slightly homestuck-y, so that everyone gets more than one *birth*, but only a single death? so like there's lots of daves running around potentially reproducing, but when Real Dave dies they all converge back into a single dead entity. Then you'd need the birth rate to be a lot higher than the death rate. but even that could change depending on how the society defines death.

Or in that case, demographically, I'd probably think of it as all the daves being one individual?

Like, on an abstract mathematical level, where you can kill someone such that more than one person is removed from the population, without there having been a previous "birth" even that correlates with each death, I can't quite get there.

I guess if you ran the deathrate-less-than-one scenario on rewind you'd get uncreated eternal people dying, but even that is more a birthrate less than 1 than a deathrate greater than 1.

That sounds a _little_ like David Brin's Kil'n People, in which most work is done by temporary copies of those most capable of performing it, while the rest of the population live on Guaranteed Basic Income (referred to as "the purple wage"), which is somewhat dystopian-ish-ly low. (High enough to prevent roving bands of disemployed people from eating the rich, but not much.) In any case, people in the privileged class are in some sense born several times over each day -- at least in any setting where economically productive activity is going on, almost all the "people" you see walking around are actually golems -- but the golems also die in the evening, as their experiences are re-absorbed into the prime copy, and the material they're composed of is recycled, so a new golem can be imprinted the next morning.

Edited 2016-05-17 07:10 (UTC)

I am in awe.

So if 1% of the population dies in a year, you need 1% of the population to have a kid that year (and it doesn't really matter which 1% that is.)

also no undying elves complaining about how their race is dying out because they only have a kid a century each

this is highly relevant to a thing I am writing thank you

Glad it can be useful!

Complaining about one-kid-a-century might make sense if you were, say, King Thranduil in the Second Age and your young people are constantly being eaten by spiders, but it makes no sense whatsoever if you are Ingwe of the Vanyar and only one of your people has died ever in all history. (Obviously those are extreme cases, and Tolkien actually does a reasonably good job with it, but a lot of the people building off of Tolkien have ...not.)

Basically it's back to you want your birth rate to basically equal your death rate in order to be stable. If you want to think about it generationally, which is easier than thinking in the large scale for me when I'm storybuilding, in a particular age cohort of immortals the percent of that cohort who have died so far should (very roughly!) equal the the percent of that cohort who have had a kid so far*. If it is significantly less, then you can start worrying about your people dying out. If it is significantly more, you should probably be sending more people out to fight the giant spiders.

*Although this only applies if your deaths and births are evenly distributed by age. If your death rate is very skewed by age - say if most people who die don't make it to their first century - you can probably give their agemates a couple more centuries to catch up with the birthing, but once the survivors have made it past the high-death-rate age, it would still pretty much apply. And if you can only have kids in your first century then the young people would have to get well ahead on the birthing.)

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The Importance of Siblings

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