circa 1667 BCE — Zeus seduces Io

One of the less lucky of Zeus’s conquests, Io was a nymph, daughter of the river god Inachus and the tree nymph Melia. One of the reasons for Io’s unluckiness was that she was a priestess of Hera – wife of Zeus and known to take a dim view of her husband’s philandering. When the two were surprised in the act of love by Hera’s approach, Zeus transformed Io into a cow (although she was later transformed back).

Her son by Zeus was Ephapus, a king of Egypt whose daughter in turn was Libya, who later slept with her grand-uncle Posiedon (brother of Zeus), and whose grand-daughter Europa, great-grand-daughter Semele and great-great-great-grand-daughter Danae would also, in their turns, be loved by Zeus and produce children by him.

Referenced in:

When You Sleep — Cake