Cerberus's parents are Echidna and who?
Cerberus:  Cerberus was the offspring of the monsters Echidna and Typhon, and usually is described as having three heads, a serpent for a tail, and snakes protruding from parts of his body. Echidna (mythology):  She was the mate of the fearsome monster Typhon, and known primarily for being the mother of monsters, including many of the most famous monsters of Greek myth.
Typhon