It's All Geek to Me:
tales of the Greek Gods by Leah Samul
Samhain 1990: Tales From The Dark Side
The Gorgons
According to Hesiod, the three daughters of Ceto and Phorcys. The most famous of these three was Medusa, who, along with her sisters Stheno and Euryale, could turn humans to stone by looking at them. If you go by Hesiod's account and consider these three to be the daughters of Ceto and Phorcys, the Gorgons were the sisters of the Graeae, Echidna and the dragon Ladon. Other sources say that the Gorgons were the offspring of Gaia, or Ge. According to this genealogy, Gaia brought forth the Gorgons to help her children the Giants in their war against the Olympian Gods. Of the three Gorgons, only Medusa was mortal. (Tripp, p. 252 [Hesiod, THEOG 270-283; Euripides, ION])
The Graeae
Their name means "grey women," and there were usually two of them. Their names were Enyo, Pemphredo, sometimes spelled as Pephredo, and Dino, variously spelled Deino. They were the daughters of Ceto and Phorcys and the sisters of the Gorgons, Echidna and Ladon. Old hags who had been grey-haired from their birth, they seem to personify age the way the Graces personified beauty and grace. They shared among them only one eye and one tooth. When Perseus was trying to defeat their sisters the Gorgons, he went to their cave and snatched the tooth and the eye and told them he would return it if they told him the whereabouts of certain nymphs, because they had weapons that he could use to defeat the Gorgons. According to Apollodorus, upon telling him this they got their tooth and eye back. (Tripp, p. 254 [Apollodorus, 2.4.2, Hesiod, THEOG 270-283; Aeschylus, PROM BOUND 794-795])