Incest appears in the commonly accepted version of the birth of Adonis, when his mother, Myrrha has sex with her father Cinyras during a festival, disguised as a prostitute.
In Ancient Greece, Spartan King Leonidas I, hero of the legendary Battle of Thermopylae, was married to his niece Gorgo, daughter of his half-brother Cleomenes I.
Greek law allowed marriage between a brother and sister if they had different mothers.
For example, some accounts say that Elpinice was for a time married to her half-brother Cimon.
The children of incestuous relationships were regarded as illegitimate, and are still so regarded in some societies today.