Iobes is the son of Herakles and Kerthe who was one of King Thespius. During his stay in the court of King Thespius Herakles impregnated 49 of Thespius' 50 daughters including Kerthe who he lay with one night. The result of that particular encounter was Iobes.
"by Kerthe he [Herakles] had Iobes
- Apollod. Biblioteca 2.7.8