Many royals and lords actually did engage in sex with their mother, siblings, relatives in order to KEEP THE BLOODLINE PURE, and not only in dynastic China. Victims of non-consensual incest are more likely to suffer disabling psychiatric problems, i.e., to be ROYALLY FUCKED from a psychological perspective.
Nonetheless, ROYALLY FUCKED is noticeably physical in nature:「In fact, the actual diseases and defects brought about by royal inbreeding were much less subtle, and often far more physical. Any psychological issues tended to be accompanied by noticeable bodily deformities, all of which ultimately rendered the victim probably infertile and completely unable to function properly in day-to-day affairs. …Charles II of Spain, for example, is infamous for having one of the worst instances of this condition on record. His jaw was deformed to such an extent that he was utterly unable to chew, and his engorged tongue, hugely swollen and enlarged, made him drool continually. He was the result of over two centuries of inbreeding, and it was noticeable. He also suffered from hallucinations and convulsions. By the 18th century, the line was so deteriorated that it became infertile, which marked the literal extinction of the House of Habsburg in 1740. …[H]emophilia became known as a disease of royalty…strange-looking heads due to having deformed skulls, strangely elongated in the back…the actual skulls found on many of Egypt's royal tombs feature this alien-like deformity. As per custom, Egyptian brothers and sisters married often, as well as mothers and sons, cousins and cousins, and fathers and daughters. …Tutankhamun (or King Tut) is one of the most famous examples—in addition to a misshapen skull, he also suffered badly from a cleft palate, club feet, missing bones, and scoliosis. …[P]roducts of incest are ultimately inviable and often lead to miscarriages or stillbirths. Incestuous relationships are therefore commonly infertile ones. But dysfunctional reproductive systems are also a usual result of constant inbreeding, where pregnancy cannot even occur in the first place. The Spanish line of the House of Habsburg, for example, went extinct with the death of Charles the Bewitched (so called because many at the time believed that his many ailments were caused by witchcraft or a curse), who died childless. …A cleft palate happens whenever the roof of the mouth does not form fully, leaving the palate open to the sinus passage. Cleft palates make swallowing, chewing and breathing difficult and prone to all kinds of complications. It also affects speech. Here, King Tut is again the go-to example…. [T]he relatively isolated Vadoma tribe in Zimbabwe, which presents a strikingly high occurrence of fused limbs in their feet—making each foot look as if it had fewer fingers. …[S]coliosis is fairly common outside of incest, inbreeding makes it significantly more likely to occur even if neither of the parents has it. …[I]nbred people are more likely to develop tumors…. Charles VI, the Mad King of France, is another famous example of realistically insane kings. When he lost his mind, he could barely understand what was going on, let alone deliberately plan to murder people. At some point, his delusions were so intense that he truly believed he was made of glass and that he could break with the slightest touch. …It is very common for children born of incest to be extremely prone to disease. Their sickly dispositions can come from a variety of causes related to inbreeding: from cranial malformations to muscular defects. But one of the biggest health issues is far more subtle: defects of the immune system.」
[ https://culturacolectiva.com/en/history/crazy-diseases-caused-by-royal-inbreeding/ 2023-05-18 ]