Rav Yankel Galinsky added the following.
Chizkiyahu Hamelech was a big Tzaddik and was worthy of being Mashiach. He became sick and Yeshayahu the prophet came and told him in the name of Hashem that he is going to die.
Why?
Because he never got married.
Chizkiyahu Hamelech explained that the reason he never married was because he saw with Ruach Hakodesh that he was going to have bad children.
Yeshayahu Hanavi answered him, "don't mix into Hashem's business. You have a Mitzva to get married!"
Chizkiyahu replied to Yeshayahu "give me your daughter as a wife, hopefully in your merit and my merit I will have good children."
Chizkiyahu got married and had a son, Menashe Hamelech.
Menashe was a big Rasha, he put an idol into the Beis Hamikdash, he killed his Grandfather Yeshayahu and caused great destruction.
He was finally captured by the King of Ashur. He was put into a huge copper pot on the fire.
Menashe saw he was in great tragedy and prayed to every idol and avoda zara to save him.
When he realized that nothing was helping he said, "I remember my father taught me the passuk that a person should Teshuva, because Hashem is merciful and He will not destroy you."
Hashem saved Menashe, he did Teshuva and was a righteous King for 33 years.
Chizkiyahu Hamelech knew that his son would be a Rasha, but even so he still learned with him and taught him Torah, and through that after many years Menashe recalled what his father taught him and returned!
