Explain the irony in the story ‘Keeping It From Harold'

Harold’s parents feared that after knowing the truth, Harold would be hurt and would not like it that his father was a professional boxer.-But the irony of the story was that, when Harold came to know about the secret, he surprised everybody by saying that he always admired ‘Young Porky’. It is ironical that he used to bet on the boxers without knowing that he , himself was the son of a famous boxer.