Joanna was from the house of Trastamara. They were known for cousin marriages throughout centuries. Her parents were second cousins. It is possible that as a result of her being a child of such a practice, she could not bear any children. Joanna was an intelligent child but could be moody. Her husband, Philip, was also a product of inbreeding. When he died, she kept his corpse and slept with it.

He was a descendant of Joana of Castile and the son to double first cousins, Emperor Franz II and Marie-Therese. Ferdinand was born with hydrocephaly. This meant he had water in his brain. Ferdinand’s disabilities meant he did not directly control matters of the state. He did like to sit on the end of a paper basket while rolling around on the floor.

Victoria’s genes were everywhere in European royalty. All of her children with Prince Albert were inbred as they were first cousins. She had hemophilia which she passed on to her kids and all throughout the bloodline. It’s a rare, recessive disease and for hemophilia to be present among the cousins, the queen may very well be the product of inbreeding.

Charles II had a severely oversized jawline common in the Habsbrug line. As a result, he could barely eat or speak. The King was known to drool a lot, and he couldn’t walk until he was 8. Even then it was difficult for him. He was married twice but did not father any children, perhaps another result of being an inbred.

Alexei Romanov is the grandson of Queen Victoria and he inherited the infamous “royal disease” hemophilia. His bled so much that it threatened his young life. This caused his mother, Tsarina Alexandira, to seek the help of Rasputin. The Romanovs’ tragic story has been well documented, as well as the life of the eccentric Rasputin.

King George III of England may have had porphyria. This genetic condition causes bouts of madness and causes the one afflicted to have purplish-bluish urine. But it was possibly just bipolar disorder. He would write differently and talk nonstop until he drooled. George also suffered from skin conditions, and thanks to his mental state, cost him the American Revolution.

Princess Victoria Melita is a granddaughter of Queen Victoria. She may not have gotten hemophilia but her bouts with headaches were something else. Melita married her cousin, Kirill Vladimirovich. The family may have insisted on intermarriages to keep the blood pure but it wasn’t always smooth sailing for the royals.

Maria I of Portugal married her uncle. Their son, Prince Joao, was her cousin. Maria the Mad was thought to be deeply religious to the point of fanaticism. She would shriek and howl accompanied by tantrums when she’d think of eternal damnation. Dr. Francis Willis diagnosed Maria as insane but none of his treatments worked.

King Ludwig II was known for being mentally unstable to the point that he was completely out of touch with the world around him. He ascended to the throne at the age of 18 but was still very much a child inside. He never carried out his duties, instead living in his fantasy world. He was deposed and murdered in 1886.

Empress Elisabeth of Austria went on to marry her cousin, Franz Josef. She was beautiful and is often compared to Princess Diana. However, she had anorexia and suffered from depression. Elizabeth was timid, shy, and nervous. She barely ate but would exercise excessively. Her son committed suicide which caused the Empress to travel around the globe before being murdered by an Italian anarchist.

Ancient Egypt was also known for inbreeding. King Tutankhamen’s parents were no exception. His mummy showed that he had a cleft palate, club foot, and elongated skull, along with persistent malaria. He wasn’t the strong boy often portrayed in pop culture. DNA study was done on King Tut. He was the product of a high level of incest. His parents were probably siblings and his compromised immunity meant he wasn’t meant to live a long life. King Tut made the same mistake of marrying his sister though.

Protestant missionaries were not happy when Nahienaena of Hawaii began to be romantically involved with her brother, King Kamehameha III. She wanted to marry him. She was expelled from the church after 1825 when the siblings married. Nahienaena was soon found to be pregnant with her brother’s child and even though she was repentant, the people shunned her. Her baby died in a few hours, possibly from inbreeding defects.

Cleopatra is celebrated as being a tough, smart, lady who charmed and seduced her way to achieve her ambitions. She’s often depicted as beautiful but as she was of the Ptolemaic period, her parents were siblings. She married both her brothers as was tradition. Cleopatra was found to have ad a hooked nose, a round face, and fat hanging under her chin. A far cry from the stunning woman history portrays her to be.

King Rama V and his harem of 153 wives, concubines, and consorts, had him fathering 77 children. He was a member of the Chakri dynasty, notorious for marrying cousins and relatives. Rama V built public hospitals, a railway, and even abolished slavery. He only showed one of his wives in public as western leaders looked down on his practices. He knew it was the incest but insisted it was just custom.

Caligula came from a family of biological relatives who would marry to keep money, power, and the bloodline pure. He was a man of lust and insatiable brutality. He forced people to witness the tortures and executions of their children. Claims of him engaging with his sisters while being cruel towards them are highly possible. Caligula was assassinated eventually by guardsmen.

Many royal families practiced inbreeding, but the Romans seem to have gotten the darker end of it. The atrocities committed and cruel practices exercised have modern scholars studying if inbreeding played a direct role. Nero watched the city burn, slept with his mother, killed her, his stepbrother and wives, and held abusive orgies in his villa. He also persecuted Christians. Nero really wasn’t right in the head.