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