Greek mythology is full of fascinating stories that have captured the human imagination for millennia. But some of the stories contain elements that may confuse or disgust modern readers. For example, many Greek gods were in incestuous relationships.
The Greek gods married their siblings out of practicality and because human standards did not apply to them. Most gods shared common ancestors. If a god didn’t want to marry a mortal, the majority of his choices were his family members.
The Greek gods are complicated and full of contradictions. The Greeks imagined their gods like humans, with human bodies and flawed personalities. But the gods were equally inhuman, held to different standards, and allowed to do things humans couldn’t, such as engaging in incest.
Also see Why Did Greek Gods Have Last Names? to learn more.
Which Greek Gods Married Their Siblings?
In the Greek creation myth, very few gods come from “nothing.” Most of them belong to a complicated family tree with shared ancestors.  The gods had very few choices for spouses outside of family members.
Greek gods who married their siblings include Zeus and Hera, Erebus and Nyx, Oceanus and Tethys, Hyperion and Theia, Coeus and Phoebe, Cronus and Rhea, and Aphrodite and Hephaestus (half-siblings). There are also examples of parent-child incest and uncle-niece or aunt-nephew incest.
Most examples of sibling incest in Greek mythology come from the Titans, the children of Gaia and Ouranos. (Ouranos happened to be Gaia’s son.) Gaia, the earth goddess, and Ouranos, the sky god, had six daughters and six sons. Four of these sons married their sisters. These incestuous marriages are:
- Oceanus and Tethys, who had thousands of daughters called the Oceanids, or ocean nymphs.
- Hyperion and Theia, parents of Helios (the sun god), Selene (the moon goddess), and Eos (the goddess of dawn).
- Coeus and Phoebe, parents of Leto and Asteria.
- Cronus and Rhea, parents of six of the twelve Olympian gods, including Zeus and Hera.
Other incestuous relationships in the Greek pantheon include Zeus and Demeter, who weren’t married. They’re both children of Cronus and Rhea, and together they had a child, Persephone. In some versions, Zeus raped Persephone, his daughter, and niece, and had a child with her. Persephone later married her uncle, Hades, who is brother to both of her parents.
Zeus also had children with his first cousin, Leto, whose parents are also siblings. He had children with two of his aunts as well, Mnemosyne and Themis.
Erebus (“Darkness”) and Nyx (“Night”) are both children of Chaos, the void from which all things began. These siblings have two children together, Aether (“Heaven”) and Hemera (“Day”). Nyx and Erebus are among the first gods in the Greek creation myth, so they likely entered a relationship out of practicality, as there were no other choices.
It’s also worth noting that the older Greek gods were often representations of concepts, like Darkness and Night. The Greeks may not have viewed Erebus and Nyx as literal siblings, just two concepts that sprang forth from Chaos.
Also see Why Are Greek Gods Depicted As White? to learn more.
Why Did Zeus Marry His Sister?
One important element of many ancient mythologies is the hieros gamos, or holy marriage, between a sky god and an earth goddess.  This union often represents the meeting of masculine and feminine ideals, and the marriage brings fertility and blessing to worshippers.
Zeus married his sister to fit the archetype of the hieros gamos. He’s a sky god, and she’s the goddess of several feminine domains, including the household, family, and childbirth. Hera may have had origins in an ancient earth goddess, making her even more appropriate as Zeus’s wife.
Greek mythology features three major sky god-earth goddess marriages, all of which happen to be incestuous. Gaia married her son Ouranos, their children Cronus and Rhea married, and their children Zeus and Hera married. All three of these marriages produce several important mythological figures.
Perhaps the incest of these marriages was secondary to the symbolism of the sky god and earth goddess. Perhaps the Greeks needed the ruling married pair of their pantheon to be a sky god and earth goddess, and the two most appropriate gods happened to be siblings. The Greeks put aside their distaste for incest so that the sky and earth could unite and bless the world with fertility.
Another theory why Zeus married his sister is that the Greek belief system adopted myths and gods from other religions, combining their mythologies. Perhaps one religion depicted a sky god married to the goddess of marriage, while another depicted the two as siblings. When different mythologies combined, Zeus’s wife and sister may have become the same figure.
Also see Did Greek Gods Come Before Christianity? to learn more.
What Did the Ancient Greeks Think of Incest?
The incest in the ancient Greek religion may cause a modern reader to think the Greeks condoned or even encouraged incest. But this could not be further from the case. The Greeks didn’t like or encourage incest, regardless of how their gods acted.
The ancient Greeks were disgusted by incest in humans. Stories about incest in human families are tragedies. However, these hang-ups do not appear to apply to the Greek gods.
The most famous example of incest in ancient Greece is the story of Oedipus, told by the playwright Sophocles. Oedipus is prophesied to kill his father and marry his mother. Despite his and his parents’ attempts to avoid the prophecy, Oedipus unknowingly murders his birth father and marries his birth mother.
When Oedipus’s true parentage comes to light, he’s so disgusted that he tears out his own eyes. His mother and wife, Jocasta, kills herself. Oedipus ends the play in exile, overwhelmed by his guilt.
The ancient Greeks didn’t condone incest. They viewed it on par with patricide, one of the worst possible sins. Even though Oedipus commits incest unknowingly, he’s still held accountable and shamed for his actions.
However, the Greeks may not have considered all kinds of incest on the same level. One of Oedipus’s daughters was engaged to her first cousin, and Sophocles doesn’t condemn the relationship. The Greeks didn’t know much about the genetic ramifications of inbreeding, so marriages between cousins don’t seem to be discouraged.
The Greeks condemned most incest, but the gods lived by different rules. The marriage between Zeus and Hera was a contradiction, both incestuous and holy.
Also see Why Do Greek Gods Have Small Genitals? to learn more.