Incest—sexual relations between close biological relatives—might make most of us squirm, yet it has been a recurring practice across many cultures throughout history. Royal families, in particular, often intermarried to preserve a “pure” bloodline and to safeguard the throne both politically and economically.
Attitudes toward incest have varied wildly; some societies warned of supernatural curses for such unions, while others viewed them as a sacred duty or even a form of worship. The worldwide examples below reveal just how diverse and surprising these customs can be.
10. Fascinating Cases: Historical Incest Overview
10. Ancient Africa
In the bygone Kingdom of Mutapa, located in present‑day Zimbabwe, a monarch boasted over three hundred wives. His “principal” spouses were often his own sisters or even his daughters, and only their offspring were eligible to inherit the throne, keeping the royal line untainted by non‑royal blood.
The practice of royal incest also appeared in the Fon kingdom of Dahomey (now Benin), where the king could take any woman he desired—single, married, foreign, native, free, or enslaved. Female relatives such as cousins were permissible, though full sisters were off‑limits.
9. Ancient Egypt
Pharaonic Egypt held the belief that a royal heiress’s dowry included the very throne itself, and that sibling unions would fortify the bloodline. Numerous 18th‑dynasty pharaohs married sisters or half‑siblings, and the 19th‑dynasty ruler Ramses II certainly followed suit.
Akhenaten, also known as Amenhotep IV, wed his sister Nefertiti, and some scholars suggest his parents were themselves close relatives. Artistic depictions hint at genetic irregularities, later confirmed by DNA analysis of his son Tutankhamun, indicating that long‑standing brother‑sister marriages likely introduced harmful mutations.
8. Roman Egypt
When Rome ruled Egypt, incestuous marriages flourished among non‑royal citizens, even as Roman law frowned upon such unions. Records show ordinary Egyptians marrying brothers to sisters, defying the imperial moral code.
These marriages cut across social strata, with the most astonishing case involving a pair of twins who produced an heir. The phenomenon was especially prevalent among the Greek settler community, where a limited pool of partners may have encouraged such pairings.
7. Zoroastrian Iran
Before the Muslim conquest, Zoroastrian Iran embraced incestuous unions as a sacred act, believing that marriage mirrored divine worship. Texts from the sixth to ninth centuries AD describe mother‑son, brother‑sister, and father‑daughter marriages as spiritually potent.
Such relationships were thought to pave a path to heaven and cleanse the soul of sin. While concrete archaeological evidence of these practices is scarce, religious manuscripts repeatedly reference the theological legitimacy of incest in Zoroastrian doctrine.
6. Europe
From the 15th through the 19th centuries, European royalty frequently married cousins to consolidate power. The Spanish Habsburgs, Prussian Hohenzollerns, French Bourbons, Russian Romanovs, and the British royal family all practiced close‑kin marriage.
Scholars argue that the Habsburg dynasty’s decline was accelerated by inbreeding, which manifested in both mental and physical ailments that weakened the family’s political standing.
5. Madagascar
Anthropologists studying the Malagasy have uncovered a patchwork of incest definitions. In some regions, first‑cousin marriages are accepted, while elsewhere they are strictly forbidden.
Crossing the incest line—whether intentional or accidental—is believed to invite calamities: failed crops, capsizing canoes, child mortality, female infertility, and even birth defects such as horns or humps. These misfortunes are thought to affect the entire community, prompting ritual atonement to restore balance.
4. The Incas
The Inca regarded themselves as descendants of celestial deities, mirroring the myth of the Sun marrying the Moon. Consequently, royal siblings were expected to wed, merging paternal and maternal claims into a single heir.
If a marriage failed to produce offspring, the king would sequentially marry additional sisters, and in the absence of sisters, a first cousin would be selected to preserve the perceived purity of the lineage. Spanish conquest ultimately ended this practice.
3. Polynesia
Among Polynesian elites, a brother‑sister union was thought to endow the child with extraordinary mana—spiritual power and prestige—making the offspring virtually untouchable in succession disputes.
19th‑century Hawaiian scholar David Malo described this “loop, a thing bent on itself,” where chiefs married sisters, half‑sisters, or nieces to keep the bloodline as high‑ranking as possible. The resulting child was deemed divine, ensuring an uncontested claim to leadership.
2. Thailand
Thai monarchs historically maintained extensive harems that often included close relatives. In 1907, King Chulalongkorn (Rama V) married two half‑sisters as queens, seeking an heir of the highest dynastic rank.
Incest was not legally barred for non‑royals, and royal “kingmakers” arranged unions between uncles and nieces or half‑siblings to maximize political legitimacy. The king’s father fathered 84 children with 35 wives, illustrating the scale of intra‑family alliances.
1. Tibet
In Tibetan culture, incest is a taboo rarely spoken of, yet when it occurs, a special pilgrimage to the sacred mountain Chorten Nyima is performed to cleanse the couple’s sins. The Tibetan term “nal” directly translates to “incest.”
Tibetologist Katia Buffetrille recounts a 1989 incident where a village couple, caught in an incestuous act, were beaten and then escorted to Chorten Nyima. After bathing in the holy lake and spring, they received a sealed certificate from a monastery confirming their purification.
Following the ritual, the couple returned to their families and reclaimed their previous social roles. If the male held higher status, his mother would accompany him, while the female’s father would accompany her on the pilgrimage.
Researcher Alexa MacDermot, based in Ireland, notes that the ritual’s completion removes stigma, allowing the pair to reintegrate without lasting shame.