His birth details are a bit vague. But he sprang from the soil, making him the son of GAIA, although for some reason he did turn out half-man and half-serpent.
This did not stop him becoming founding the city of Athens and marrying AGLAURUS, who bore him a daughter of the same name, plus two more girls, Herse and Pandrosos, and a son, Erysichthon. He also attempted to adopt the snake-baby ERICHTHONIUS as a favor to GAIA, but this turned out to be something of a mistake.
During his reign there was a dispute between ATHENA and POSEIDON over the patronage of Attica. CECROPS was asked to mediate. POSEIDON had caused the sea to form a harbor, but ATHENA had planted the first olive tree.
CECROPS decided the new fangled olives were best. This caused POSEIDON to froth at the mouth and cause a nasty tidal wave. This proved a point. Sea was dangerous stuff, whereas olives were a splendid trading commodity, especially in the form of oil.
Wise old CECROPS ruled really well. He established writing, marriage laws and all sorts of civilizing influences and did away with human sacrifices. He built the city of Cecrops which later became Athens.