Incest is mentioned and condemned in Virgil's Aeneid Book VI:[REF] hic thalamum invasit natae vetitosque hymenaeos; "This one invaded a daughter's room and a forbidden sex act".
In Norse mythology, there are themes of brother-sister marriage, a prominent example being between Njörðr and his unnamed sister (perhaps Nerthus), parents of Freyja and Freyr.