Question

Whose son is Theseus?

Answer 1

Aegeus 
Aegeus is the father of Theseus
 Aegeus was an archaic figure in the founding myth of Athens
he was also the founder of Athenian institutions and one of the kings of Athens

Answer 2

Heya,

According to Greek mythology Hippolytus was the son of Theseus and Aegeus was the father of Thesus. Theseus was regarded as a founding hero.  Hippolytus is the son of Amazon queen Hippolyta.