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Which king married with his sister?

Incestuous marriages between royal family members were not uncommon in ancient royal dynasties around the world. The most well-known example is that of the ancient Egyptian pharaohs, many of whom married their sisters or other close female relatives to keep the royal bloodline pure. However, there are a few other historical cases of kings marrying their sisters as well.

Ancient Egypt

In ancient Egypt, it was common for pharaohs to marry their sisters or half-sisters. This tradition likely started during the early dynastic period in Egyptian history, from around 3100-2700 BCE. Some examples of Egyptian pharaohs who married their sisters include:

  • Pharaoh Menes – Founder of the first dynasty of Egypt, married to Queen Neithhotep who may have been his sister or half-sister.
  • Pharaoh Djoser – Builder of the Step Pyramid, married to Hetephernebti who was his sister.
  • Pharaoh Khafra – Builder of the second largest pyramid at Giza, married to Queen Khamerernebty who was his sister.
  • Pharaoh Tutankhamun – The famous boy king, married to Ankhesenamun who was originally his half-sister.

This tradition continued for over 3000 years, with the last ruler from the Ptolemaic dynasty, Cleopatra VII, also marrying her brother Ptolemy XIII. These incestuous marriages were seen as a way to preserve the royal bloodline and strength of the pharaonic dynasties. The pharaohs were considered god-kings, so keeping the rule within the family was important politically and religiously.

Inca Empire

The Sapa Inca who ruled over the Inca Empire in South America also practiced incestuous marriages to keep the royal bloodline intact. Several Inca rulers married their full sisters, known as “Coya.” Some examples include:

  • Manco Capac – Legendary first Sapa Inca, married to his sister Mama Ocllo.
  • Sinchi Roca – Second Sapa Inca, married to his sister Mama Cura.
  • Lloque Yupanqui – Sixth Sapa Inca, married to his sister Mama Ocllo.
  • Mayta Capac – Eighth Sapa Inca, married to his sister Mama Tacucaray.

These royal incestuous unions were seen as natural and even divinely inspired. Keeping the royal bloodline intact was critically important in Inca culture and religious beliefs. The Coya held an important position and title within the empire as well.


In ancient Hawaii, incestuous marriages were also practiced among royalty to maintain purity of the bloodline. Marriages or sexual relations between brothers and sisters of royal lineage were permitted. Some examples of Hawaiian royals who married family members include:

  • Piʻilani – 15th century Maui king who married his sister Hinakaimauliʻawa.
  • Keaweʻīkekahialiʻiokamoku – 16th century Big Island king who married his niece Akahiakuleana.
  • Kalaniʻōpuʻu – 18th century Big Island king who had children by his niece Keōuawahine.

These types of unions were sanctioned to ensure the highest born offspring and preserve the sanctity of the bloodline. Over time, incest became less common among Hawaiian royalty, though it was still practiced occasionally up until the early 1800s.

Pre-Columbian America

In addition to the Incas, some other pre-Columbian civilizations in North and South America also permitted incest marriages between brothers and sisters of elite or royal families. These included:

  • The Aztec emperor Moctezuma II married his sister Princess Isabel Moctezuma.
  • The Zapotec King Clummox married his sister Copalcua.
  • The Toltec emperor Topiltzin Ce Acatl Quetzalcoatl married his sister Chimalman.

Allowing incestuous unions was likely meant to consolidate power within the royal bloodlines of these civilizations. It also may have served religious purposes, just as it did in ancient Egypt and Peru.


In Thailand, there is a long history of kings marrying their sisters or half-sisters. This was done to preserve the purity of the royal bloodline and strengthen ties within the dynasty. Some examples include:

  • King Chairacha of the Sukhothai Kingdom married his sister Queen Nang Suang.
  • King Prasat Thong of the Ayutthaya Kingdom married his half-sister Queen Aiyakesiri.
  • King Rama I married his half-sister, later becoming Queen Amarindra.

This practice declined in the 19th and 20th centuries but there were still occasional cases like King Vajiravudh who was rumored to be in love with his sister Princess Valaya Alongkorn.


While less common in medieval Europe, some examples of royal incestuous marriages exist:

  • Holy Roman Emperor Henry IV married his second cousin Agnes of Waiblingen.
  • King Alfonso X of Castile attempted to marry his sister Violante but was prevented by the Pope.
  • King Andrew III of Hungary was born from an incestuous union between Duke Andrew II and his sister-in-law Tomasina Morosini.

Incest was strongly tabooed by the Christian church so these types of marriages were very controversial. But some royals engaged in them anyway to try to protect inheritance claims or maintain a “pure” bloodline.


Marriages between brothers and sisters occasionally occurred among Indian royalty as well, including:

  • Chandragupta Maurya reportedly married his sister in the 4th century BCE.
  • King Bimbisara of the Haryanka dynasty married his sister Chellana.
  • King Rudrasena of the Vakataka dynasty married his sister Prabhavati.

These may have represented attempts to preserve royal bloodlines or consolidate power. However, Hindu texts and doctrine strongly opposed incest, so it was likely highly controversial.


In the Persian Empire, some members of the Achaemenid dynasty are known to have married their sisters or half-sisters, including:

  • Darius the Great married his sister Atossa.
  • Xerxes I married his sister Amestris.
  • Artaxerxes II married his sister and half-sister Statira.

Again, keeping the royal bloodline intact and preserving the power of the dynasty was likely a key motivation for these types of unions.


In ancient Japan, there are also a few contested cases of potential incest marriages among royalty:

  • Emperor Suinin may have married his sister Ikata-hime-no-mikoto
  • Emperor Kimmei may have married his sister Iwanohime
  • Emperor Bidatsu may have married his sister Okinagatarashi-hime

However, strong taboos eventually developed against brother-sister marriages. They were explicitly banned later on within the Japanese imperial family.

Ancient China

There are also some accounts of possible incestuous marriages among royalty in ancient China, including:

  • King Cheng of Zhou married his sister Qi Jiang
  • King Goujian of Yue married his sister Yaoji

As in Japan and India, these types of marriages may have occurred but were controversial and seen as taboo. Confucian teachings opposed incest as going against principles of filial piety.


In summary, ancient Egyptian pharaohs most frequently practiced marriage between royal brothers and sisters, as did the Inca civilization. But there are also examples found through history in Hawaii, pre-Columbian America, Thailand, India, Persia, China and other locales. These incestuous unions were likely driven by desires to maintain purity of royal bloodlines, consolidate political power, and sometimes for religious reasons. However, in many ancient societies incest eventually became tabooed or even explicitly outlawed.

Key Facts

  • Incestuous marriages occurred most commonly and openly in ancient Egypt and the Inca Empire.
  • Royals marrying sisters, half-sisters, or other close relatives was seen as preserving the purity of the bloodline.
  • Religious beliefs about divinely chosen rulers also motivated incest in some civilizations.
  • The practice became more taboo over time in many parts of the world.
Civilization Examples of Rulers Who Married Relatives
Ancient Egypt Pharaohs Menes, Djoser, Khafra, Tutankhamun
Inca Empire Manco Capac, Sinchi Roca, Lloque Yupanqui, Mayta Capac
Hawaii Piʻilani, Keaweʻīkekahialiʻiokamoku, Kalaniʻōpuʻu
Aztec Empire Moctezuma II
Zapotec Civilization King Clummox
Toltec Civilization Topiltzin Ce Acatl Quetzalcoatl
Thailand King Chairacha, King Prasat Thong, King Rama I
Holy Roman Empire Henry IV
Medieval Hungary King Andrew III
Ancient India Chandragupta Maurya, King Bimbisara, King Rudrasena
Persian Empire Darius the Great, Xerxes I, Artaxerxes II

This table summarizes some of the key civilizations and rulers who practiced incestuous marriage between close relatives like siblings.

Historical Context

When evaluating the practice of royal intermarriage in ancient civilizations, it is important to consider the historical and cultural contexts that may have motivated these behaviors. Some key points of context include:

  • Limited gene pool – Many royal classes were small and heavily interrelated. Marriage options were limited.
  • Maintenance of bloodline – Belief that keeping lineage “pure” maintained divine right to rule.
  • Political strategy – Marriage cemented alliances and prevented claims from competing dynasties.
  • Religious beliefs – Gods were thought to favor family dynastic succession in some religions.
  • Cultural traditions – Persistence of customary marriages between cousins or other kin in some regions.

Additionally, characteristics like genetic disorders from inbreeding were not well understood scientifically. Taboos surrounding incest also varied greatly by culture and were not universal.

Modern ethical objections to incest stem from concerns about biological problems from inbreeding, as well as power dynamics within families. But ancient societies did not analyze incest through this moral lens. For many ruling dynasties, preserving bloodlines took precedence over any taboos against close kin marriages.

Overall, the historical context shows why royalty practiced incest despite some religious and cultural prohibitions. Their motivations centered on dynasty succession and strength, though outsiders likely viewed such marriages as scandalous or immoral.

Lessons for Today

The practice of incestuous marriage among ancient rulers provides some important lessons that remain relevant today:

  • Bloodline and family are not the only legitimate sources of power or sovereignty. Authority should derive from the consent of the governed.
  • Scientific knowledge should inform ethical standards. Incest raises biological concerns that ancient civilizations overlooked.
  • Cultural traditions alone do not justify practices that violate human rights or dignity today.
  • Outsider perspectives provide important insight. Royal incest offended many subjects and foreigners.
  • Leaders must adhere to high ethical standards. Royal classes often violated taboos binding common people.

In the modern era, incest faces near universal taboo for good reason. But re-examining its historical practice highlights vital ethical lessons about how leaders ought to wield power. It also shows how advancing science and human rights continue to shape moral standards.

Looking critically at the past, instead of glorifying it, helps inform society’s progress towards greater justice and dignity for all.