Poseidon/Neptune is the only surviving son of Cronus after Hades/Pluto was sent to the grave. Jupiter was never a real son of Cronus.
The Targum renders this Givatai, a variation on the name Gipt or Egypt, (origin of the word Coptic, evidently denoting the ancient language of Egypt) (cf. Megillah 18a, Sanhedrin 115a). Josephus, however, attempts to render the word of G-d obsolete by stating that all the nations in this verse are unidentifiable.
