The incest taboo is and has been one of the most widespread of all cultural taboos, both in present and in many past societies.
(Genesis -35) According to the Book of Jubilees, Cain married his sister Awan.
For example, Tutankhamun married his half-sister Ankhesenamun, and was himself the child of an incestuous union between Akhenaten and an unidentified sister-wife.
It is now generally accepted that sibling marriages were widespread among all classes in Egypt during the Graeco-Roman period.
Loki in turn also accuses Freyja and Freyr of having a sexual relationship.
According to Genesis of the Hebrew Bible, the Patriarch Abraham and his wife Sarah were half-siblings, both being children of Terah, but with different mothers.