Oedipus the King
Analysis: Steaminess Rating
Exactly how steamy is this story?
PG for Oedipus sleeping with his Mom
The fact that Oedipus marries, sleeps with, and has four children with his mother gives rise to terms such as the Oedipus Complex... and is probably the best known element of the Oedipus trilogy.
However, although incest is going on, there's no sex during any of the three plays. Still, it's probably not a sterling idea to see a performance of this play as part of a Mother's Day outing.