In Greek mythology there are many examples of sexual unions between male gods and mortal women. Homer, Iliad
6.198-199, mentions one (tr. Richmond Lattimore):
Laodameia lay in love beside Zeus of the counsels
and bore him godlike Sarpedon of the brazen helmet.
Ambrose Bierce takes an irreverent look at such unions in his poem Not Guilty
"I saw your charms in another's arms,"
Said a Grecian swain with his blood a-boil;
"And he kissed you fair as he held you there,
A willing bird in a serpent's coil!"
The maid looked up from the cinctured cup
Wherein she was crushing the berries red,
Pain and surprise in her honest eyes
"It was only one o' those gods," she said.