There were periods of time in some Eurasian cultures in which the youngest son, rather than the oldest son, inherited everything, a practice called "ultimogeniture" which is consistently attested as a practice many places in Slavic Europe, pretty much through the Industrial Revolution, and is also implied or alluded to in the legendary histories of both Indo-European and linguistically Semitic peoples.
The author of the Old European culture blog grasps at ways to explain this outcome. I would offer a variation on these theme.
Perhaps established adult sons were capable of fending for themselves in the societies where this practice developed, at the time of their parents' death, because inherited wealth wasn't terribly important in these economies or there was a practice of making lifetime gifts to older children when they became adults and established their own households. But if these economies were based more on labor than on capital wealth, then the wealth of dying parents wouldn't have been substantial enough to have much impact if divided among all of the sons.
The fact that this was mostly an urban practice at its Western European extent, in towns where commerce and labor were economically important, unlike rural farmers for whom inherited land was most important, supports this analysis.
However, the least well established youngest son who might be only a young adult, or even an adolescent when his parents died, might be the most likely to need economic life support through an inheritance (and the mostly likely to still be at home, giving the youngest son a logistical edge in controlling the inheritance as well), and out of fairness would have received the least benefit from lifetime gifts from a parent. In the pre-birth control world, the youngest son might have been born with parents in their late 30s or early 40s, and the life expectancy for adults in that era was probably around their 60s.
Life expectancy at birth was often 25 to 35 years, but infant and child mortality was high, and people who survived to adulthood could live to as long as about 70 under ideal conditions. In crude averages, typical people had four or more children children, a quarter of whom died as infants, a quarter of whom died as children or young adults, sometimes after having children and sometimes not, and the rest of whom who survived well into adulthood. Only a little more than half of children born in premodern times survived to adulthood and had surviving children.
Some semblence of ultimogenitor, if the parents die before all of their children have reached middle age, is a not uncommon way for trusts for the benefit of the children of upper middle class modern families to be handled (something I do regularly in my day job as an attorney).
There is a peculiar plot found in many Eurasian fairytales: Brothers (mostly three) have to complete a task (like kill a dragon), which will get them a princess and a throne...And all the brothers fail, except the youngest, who gets both the girl and the throne...German: The Queen BeeIranian: SimorghOne interpretation of this fairytale plot is that it describes Ultimogeniture, the inheritance practice in which all the family land and the family house is inherited by the youngest son...The fact that this plot is found in stories from Europe to Central Asia is very interesting, because in most parts of Eurasia in the past it was the oldest son who inherited all the property or the property was split equally between all the sons...There were some exception to this rule though:1. SlavsUltimogeniture was particularly prevalent in Russia, where it was enshrined in law in The Pravda Russkaya, or Yaroslav’s Law, written ca. 1017 AD by Yaroslav the Wise.... . .Ultimogeniture was recorded in the 18th and 19th century in many Slavic countries like Russia, Poland, Serbia...2. MongolsAmong Mongols, Ultimogeniture (the inheritance by the youngest son) was practiced in combination with Primogeniture (the inheritance by the oldest son) and several other inheritance rules. Which caused chaos...3. "Some people" from England, Eastern Germany, Denmark, AustriaUltimogeniture was also practiced in certain parts of England where it was called "Borough-English" and was by the Normans called “the custom of the English towns”...And in some parts of Eastern Germany, Denmark and Austria...The origin of the Ultimogeniture in England, Germany, Austria and Denmark is unknown...Thomas William Shore, in his 1906 book "Origin of the Anglo–Saxon race" attributed this custom "to the West Slavic tribes which were part of Anglo-Saxon invasions of Britain" and "to the West Slavic tribes who once lived in Germany, Austria and Denmark"Some have argued that this custom was brought to Europe by the Steppe nomads, like the Huns, Mongols and Turks...But I couldn't find any mention of Ultimogeniture being practiced by the Huns or Turks who both practiced Primogeniture. And as I said, Mongols had several different conflicting inheritance rules which leads me to believe that they adopted Ultimogeniture from someone else.... . .But I think that Ultimogeniture originated not in Iron Age Eurasian steppe societies, but in much earlier, Bronze Age Indo-European steppes societies...Why do I think so? Because we find Ultimogeniture at the core of the Ancient Greek myths...There, Uranus gets overthrown by his youngest son Cronus. Only to be overthrown by his youngest son Zeus.Yet the Greeks, like everyone else around them, practiced Primogeniture...So what's going on here?I believe that this practice probably comes from the times of the expansions. When elder sons were sent away to "carve their own piece of land for themselves" and the youngest was left at home to take care of the parents and the ancestral lands...Why this was practiced by some settled peoples like Slavs is not easy to explain...Interestingly David, the youngest of 8 sons, becomes the king of Jews...Joseph of Genesis also the youngest son and favoured...And Isaac...But just like Greeks, Jews practiced Primogeniture...
From the Old European Culture blog.