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