This guest post was written by our very own MikeSchilling!

There a meme that surfaces every so often (for instance, in this episode  of 30 Rock that European royalty have been damaged by centuries of inbreeding. The best real-life example of this was King Charles II of Spain, who,

was born physically and mentally disabled, and disfigured. Possibly through affliction with mandibular prognathism, he was unable to chew. His tongue was so large that his speech could barely be understood, and he frequently drooled.

Charles belonged to the House of Habsburg, in fact, he was the last Habsburg king of Spain, and a direct descendant of the first such, Charles I of Spain (almost always referred to as Charles V, since he was the fifth Holy Roman Emperor named Charles, the first being Charlemagne.)  The Habsburgs had a genius for marrying princesses and inheriting their lands when no direct male heirs were available.

Charles V was the heir of centuries of this:

  • He was the King of Spain because his father had married the eldest surviving daughter of Ferdinand and Isabella, whose  sons died young.  This also made him the ruler of the Spanish  empire in the New World. Further, Spain rules Naples, Sicily and Sardinia.
  • He was the ruler of Burgundy in France and the Low Countries (more or less the modern Benelux nations) because his grandfather had married the only child of the Duke of Burgundy
  • His brother Ferdinand I became king of Bohemia (today’s Czech Republic) and Hungary by marrying their king’s only daughter, who inherited when her only brother died without issue.
  • And in addition to all of that were the hereditary Habsburg holdings in what’s now Austria and the title of Holy Roman Emperor (more or less the overlordship of Germany.)

When you consider the amount of territory Charles V ruled, the only comparisons are to people like Alexander and Napoleon.  The difference is that they conquered it, while his ancestors married into it. The Habsburgs were not about to have this game played against them, and developed a counter-strategy: to an appalling degree, Habsburgs only married Habsburgs, culminating in poor Charles II. I’d been curious for a while just how far this went, so I built his family tree, going back four generations: just ancestors, no siblings or other spouses, to keep it simple.  When a person appear in the tree more than once (as several do), their name is followed by the same letter at each location.  Where the fourth-generation ancestors are themselves related, that’s called out.

To summarize, where for most people a tree going back this far would contain thirty-one different people, Charles’s tree contains only twenty-three.  Moreover, where normally the sixteen great-great grandparents would all be different people, none of them closely related, here we see only ten people who don’t appear elsewhere in the tree, and only four of whom aren’t closely related.  The most egregious example of inbreeding came with Charles’s parents.  His mother, Mariana of Austria, was the niece of his father, Philip IV (Philip’s sister’s daughter).  Though it’s actually worse than that, because on her father’s side, Marianna was Philip’s first cousin once removed (her father, Ferdinand I, and Philip IV were both grandchildren of Charles II of Austria.)  And it’s even worse than that, because his parents’ mutual ancestor Charles II of Austria had also married his own sister’s daughter.

Among Charles II’s afflictions was the inability to father children; on his death, this resulted in a dispute that led to the War of the Spanish Succession, which lasted thirteen years and took hundreds of thousands of lives.


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  1. I apologize for the formatting of the family tree. I have no idea how to make that WYSIWYG the way it is in the editor.

  2. Sheesh! It’s like every joke about family re-unions in Arkansas.

    • Where Mike says: “To summarize, where for most people a tree going back this far would contain thirty-one different people, Charles’s tree contains only twenty-three”, I look at my family tree and go back that far… and, yeah, I’ve got about 29ish people.

      In the defense of my ancestors, I’d like to point out that, until America, cousin marriage was pretty g-darned common in the world.

      • As far as I know, there were no questions raised about the two uncle-niece marriages shown above. On the other hand, Henry VIII of England needed a papal dispensation to marry his first wife, Catherine of Aragon, to whom he was completely unrelated by blood, because she was his elder brother’s widow. (Catherine, by the way, was Ferdinand and Isabella’s younger daughter, and thus Charles V’s aunt. One of the main reasons that the Pope wouldn’t grant Henry an annulment from Catherine, leading to his break from Rome and creation of the Anglican Church, is that her nephew was the most powerful man in Europe.)

        One more fun fact: Henry and Catherine’s daughter Mary I of England (Bloody Mary) married Philip II of Spain, whom we can see was her first cousin once removed. For once the Habsburg strategy failed, as they had no children.

        • “nephew most powerful in europe”… AND banging on the Pope’s door.

        • “As far as I know, there were no questions raised about the two uncle-niece marriages shown above.”

          To my knowledge, each one of those close marriages (uncle-niece, cousin-cousin) required an episcopal or papal dispensation; these dispensations were granted to the royal houses of Spain and Austria as a matter of course, because popes generally wanted to be on their good sides (as in the case of Henry VIII’s annulment, like you mention). (Compare this to the case of the Cardinal-King Henry of Portugal, who unexpectantly became king in 1578 when his brother’s grandson King Sebastian died childless; Henry wished to take back his clerical vows and take a wife to continue the dynasty, but Pope Gregory refused the request–because if Henry died without heir, the throne of Portugal would pass to the Habsburgs.)

          Also, see here:

          • Awesome graphic. I hadn’t traced Renata of Lorraine back far enough. Mark her as Charles V’s great-niece and change it to only three unrelated people among Charles II’s great-greats.

      • A single cousin marriage isn’t that big a problem, even for first cousins (not that I’d recommend it), done in isolation. Uncle-niece is more problematic, but what really kills the Habsburgs is that they keep doing it repeatedly.

        Parents share 50% of their genes with their children. And each child inherits a different set of genes, so, normally, they share half of what they inherit with another given sibling. So, normally, each step along a family tree reduces shared genes by 50%. A parent’s sibling shares 25%, a parent’s sibling’s child (a first cousin) 1/8, etc.

        So, normally, Philip IV would have 1/2 duplication with Maria Anna of Spain, and hence 1/4 duplication with her daughter Marianna of Austria. But, as noted, Philip is also first cousins with Marianna’s father Ferdinand III, so 1/8 duplication with him, so Marianna shares 1/16 of Philip’s genes from that side, too. Further, Philip and Maria Anna’s parents are themselves related, so in fact Philip and Maria Anna share more than 1/2 of their genes, so Marianna inherits more than 1/4 duplication from her mother. And so on and so forth.

        As a result, the cumulative inbreeding makes poor Charles II’s parents into something closer to the equivalent of a sibling or parent-child pair rather than a pair of first cousins whose ancestors are otherwise unrelated.

        • Incest in the modern world isn’t even THAT bad. But it was a REAL problem in already tight gene pools.

      • My lovely wife likes to point out the spot in my family tree (admittedly, waaaaaaay back) forks and then comes back together.

    • IIRC, your “cousin once-removed” would be one of your cousin’s children. And a second-cousin is just like a cousin except you have to go up through your great-grandparents and then back down. So there’s like ~four times as many of them.

      • Right. The ordinal is determined by the number of generations to the closest common ancestor, minus one. First cousins share common grandparents, who are two generations up. Second cousins share common great grandparents, who are three generations up.

        When the cousins are of different generations, then the ordinal is determined by the cousin separated from the common ancestor by the fewest generations, and “N times” removed is added to indicate the number of generations of difference between the cousins.

        So if you have, say, third cousins twice removed, that means that the closest common ancestors are the great great grandparents of one cousin, and the great great great great grandparents of the other cousin. You can’t call them “fifth cousins, twice removed,” because the ordinal is determined by the cousin from the earliest generation, the one who is their great great grandchild.

        • Yes, all very logical once you know the rules. The one that bothers me is great-uncle being the same generation as grandfather, great-great-uncle being the same generation as great-grandfather, etc. It’s confusing.

      • That’s right. First, second, third refers to distance separated from a common ancestor for people of the same generation; once, twice, thrice removed refers to how many generations apart you are.

  3. To be fair…

    The Hapsburgs were then only replaced by the Bourbons, marginally better, perhaps…but really….

  4. Royalty, in general, tended to select for particular types of people (alpha males, in the main). These people, from the get-go, were predisposed towards some variants of mental illness.

    Sociopathy and Paranoia were general survival traits, after all. But even a good handful of generations of crossing these folks together, and you start seeing schizophrenia popping out, and a good few other things.

  5. What’s the deal with the variant spellings? I’m used to seeing stuff like that with Chinese, where there are different systems of romanization, but weren’t they using the Latin alphabet back then? Was dyslexia one of the recessive traits the incest brought out?

  6. I have a lot of favorite things about the Hilary Mantel books, but one of them is the looming presence of Emperor Charles, who never even appears.

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