Final answer:
Leontes blames Hermione's supposed 'sin' for his son's illness.
Step-by-step explanation:
Leontes blames the supposed 'sin' of Hermione, his mother, for Mamillius becoming ill after Hermione is put in jail. He believes that the stress and anguish caused by Hermione's supposed infidelity and betrayal is responsible for his son's illness. This demonstrates Leontes' unfounded jealousy and irrationality.
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