Jokes about inbreeding and incest are common in discussions about royalty, for non-historians such jokes can actually be some of the basis of their knowledge about royalty. However why royalty decided to choose incestuous unions and what the effects of such unions are less considered. This is despite incest and inbreeding being apparent across the world and history.
So why did royalty decide to marry relatives? The most simple and common answer was political stability. The offspring of two relatives who had strong individual claims to the throne would have an even stronger claim themselves, which theoretically should lead to an easier pass over of power. This was apparent with Incan emperors who went to the extreme of marrying their sisters, those who had the next best claim, to produce heirs. Thai kings married their half-sisters instead of their full blood sisters for the same reason. Such actions were not restricted to brother-sister marriages. Emperor Claudius married his niece Agrippa the Younger to strengthen his own claim as emperor. In Europe, many royals married cousins, although some, the Habsburgs in particular would have even more incestuous unions to strengthen their dynasties and political stability. Philip II of Spain married his niece Anne of Austria as his fourth wife. Of his three previous marriages one had been to his first cousin and one to his first cousin once removed, only Elizabeth of Valois was more distantly related. Philip IV of Spain married his niece Mariana of Austria and produced the sickly Charles II. While it did produce stability it did have ill effects on their health. However it is important to realise it was not a guarantee of political stability as infighting still would happen within families. The Ptolemy dynasty of Pharaohs is one example, instead of killing rival claimants from other families; they would often kill family members who were claimants.
Another, less common, reason for inbreeding was the ‘sacredness’ that such offspring would have this. This is apparent in societies where royalty were considered to be gods. For Pharaohs, incest meant that the sacred blood line was kept pure, which considering the emphasis placed on Pharaohs being gods was extremely useful. This was to the extent that in Cleopatra’s family tree only six individuals make up her sixteen great grandparents. In Hawaii inbreeding was preferred and sometimes even obligated for royalty. The child of two full blood siblings was considered to have the highest ‘mana’, meaning the most sacred. Avuncular relations, those between an aunt/nephew or uncle/niece were also accepted for similar reasons.
There was also the case that by a certain point with European royalty that almost everyone was related due to such a small pool of people who were considered eligible. However the effects of inbreeding were lessened somewhat as unions were not always within the first degrees of relation. For instance Henry VIII was related to all his wives however he was no closer than third cousins with any of his wives and in the case of Anne of Cleves they were ninth cousins.
The basis of many jokes about royalty and incest are that of the effects they have on the offspring of royalty. Surprisingly there does not always seem to be as many ill effects as one would imagine, especially in the case of brother-sister offspring. Although in some countries there may have been due to reliance on oral history which could mean such issues may not have been recorded. However there are two prominent cases of how disastrous inbreeding could be on health. The first is that of Tutankhamun who has been proved to be the product of incest. Work on his mummified body has shown that images of him in his tomb were far from accurate of what he looked like. Physically he had a club foot, which would have prevented him being able to stand independently; severely limiting activities as a Pharaoh he should’ve been able to participate in such as chariot racing. He also had an extreme overbite and what has been described as ‘feminine hips’. He also suffered from conditions such as Kohler’s disease and epilepsy. These problems are thought to have hastened his early death.
The second is the Habsburg family. While as previously mentioned above, intermarriage was practiced by all the European royal families, the Habsburgs took it up a notch. Family members married other close family members, such as their first cousins and as mentioned above there were several avuncular marriages. Such inbreeding led to the infamous Habsburg jaw which caused severe pain and a number of medical issues that made simple tasks such as eating difficult for those who were inflicted with it such as Charles V and Ferdinand I. The Habsburg jaw can still be seen in the Spanish royal family today, although in a much less exaggerated form. However the real victim of Habsburg inbreeding was Charles II of Spain, whose numerous difficulties are thought to have been the result of this inbreeding. He was unable to speak till the age of four and walk until he was eight. He is now believed to have suffered from two genetic disorders: combined pituitary hormone deficiency and distal renal tubular acidosis both of which do not allow the body to properly function. He was also infertile and failed to produce an heir which led to the extinction of the senior branch of the Habsburg family.
Incest was practised widely across the world by royal families, although the reasons and to what extent such incest was practised varies. Similarly the effects that inbreeding had on royalty has also varied, which somewhat challenges our preconceived ideas of what the results would be. Thankfully royalty these days generally don’t practise such close consanguinity.