Ancient Egyptian royal bloodlines were flush with incestual relationships. The ancient Greek word philadelphoi, later adapted to Philadelphia, was coined for the brother and sister marriage between Ptolemy II and Arsinoe. The city of brotherly love takes on a whole new meaning now, doesn't it?
The ancient Egyptians were so into keeping their bloodlines "pure" that they even came up with a cute little name for when a man married his brother and sister's daughter. They called it a "double niece" marriage. Pretty disgusting.
One of the most famous names of ancient Egypt, King Tut, was also a product of incest. His parents were brother and sister and it's thought that Tut also married his sister Ankhesenamun. Scientists found mummified stillborn babies in his tomb whose DNA had parents who were related.
King Tut was plagued with illnesses his whole life. He had a cleft palate, scoliosis and a club foot, all likely caused by the limited gene pool he was exposed to. A far cry from the portrait that was painted by Egyptian royals.
During the rule of the Hawaiian monarchy, Princess Nahienaena was encouraged to follow royal tradition and marry her brother Prince Kauikeaouli, later called Kamehameha III. But Nahienaena didn't need encouragement because legend has it that her and her brother were deeply in love.
Once Christian missionaries descended upon the people of Hawaii, they encouraged Nahienaena not to marry her brother, but she refused. Nahienaena and Kamehameha III became pregnant and were shunned by the ever-growing and powerful church.
In an attempt to win back the approval of the church and her people, Princess Nahienaena then married a non-family member, Chief Kalanimoku's son. However, the church did not take her back and Nahienaena gave birth to her brother's child only to have it die a year later. Overcome with grief and anxiety, Princess Nahienaena died shortly after.
Like many royals, Queen Victoria believed that inbreeding kept the royal bloodline strong. While she was wrong for a number of reasons, the main reason she should have hopped off of the old incest bandwagon was her hemophilia. Hemophilia is a disorder where your blood doesn't clot properly, which can cause excessive bleeding or death when a person is injured.
Queen Victoria married her first cousin, Prince Albert, who also had hemophilia. Together they passed that gene down to their eight children and then married them off to gain control over the rest of Europe. According to reports, many of their decedents died because of this this.
While inbreeding is out of the Royal Family for now, thanks to Price William and Catherine, Duchess of Cambridge, it wasn't so long ago that this was still considered okay. Queen Elizabeth is married to Prince Philip, Duke of Edinburgh, her third cousin.
The Habsburg dynasty has to be one of the most disturbing cases in royal history in terms of proving how incest can ruin future generations. While it was custom for centuries for royals to marry relatives, the Habsburg family ruined their reign through incest.
The House of Habsburg was arguably one of the most powerful families in royal history. They reigned over Europe for centuries and gained control over Switzerland, Hungary, Austria, France, Italy and Spain, but by the 17th century, their bloodline ran thin as it was riddled with inbreeding.
After centuries of first cousin, uncle and niece and even brother and sister marriages, members of the Habsburg family were deformed, mentally ill and infertile. The most severe case of this, and what led to the family's demise, was their final heir to the throne, King Charles II.
King Charles II was named El Hechizado (The Hexed) and was the result of an uncle and niece union, who were also results of a long line of incest. According to reports, King Charles was mentally retarded, disabled and disfigured. He also suffered from multiple physical ailments such as sporadic hematuria, the inability to walk until age eight and severe weakness his entire life.
Along with being sick his entire life, King Charles was impotent and infertile. He married twice but was unable to produce an heir to the throne. Upon his death at age 39, the Habsburg dynasty was left with no male heir and the kingdom was left to members of the House of Bourbon.
In a twisted turn of events, keeping their bloodline pure ended up becoming the catalyst for the demise of a dynasty.