The demigods have done nothing wrong were Hercules, Perseus, Orpheus.
Parents of Orpheus: Apollo and Calliope (mortal)
Apollo gave him a lyre made from this crib and the nine strings were honor by the nine Muses. The Muses took him under their wing. They teach him music and poetry. With the help from Orpheus and his powerful lyre, he assists Jason of Thessely to retrieve the Golden Fleece.
Parents of Perseus: Zeus and Danae (mortal)
His grandfather, Acrisius the King of Argos, fear of Perseus someday he'll kill him. That's what the Oracle of Delphi told his fate. So he imprisoned his daughter Danae in the tower as long as no man in Argos will impregnate her. Until one day King Acrisius over heard the cry of a baby from the tower. Danae told him it's Zeus impregnate her when Zeus transform into golden rain fall upon her when she asleep. King Acrisius didn't believe her and blame on the innocent nurse who's with Danae. He blindly accuse the nurse that she secretly bring in a man. So the King had her beheaded. He requested the great carpenter to make a casket for Danae and her baby. The King's men push her away to the sea. When Perseus grew up, the Gods assist him on his journey to the underworld and behead the Medusa.
Parents of Heracles: Zeus and Alcmene (mortal)
Zeus the horny dog order Apollo to turn day into night and order Hermes to cast a sleeping spell upon King Amphitryon so he may bed with his beautiful queen Alcmene. He named his son Heracles after his wife Hera to appease her for approval. What an idiot.