Question: Cerberus's parents are Echidna and who?
Sentence (from "Orthrus"): In Greek mythology, Orthrus (Greek: Ὄρθρος , "Orthros") or Orthus (Greek: Ὄρθος , "Orthos") was, according to the mythographer Apollodorus, a two-headed dog who guarded Geryon's cattle and was killed by Heracles.
Relevant evidence: No