Final answer:
In Macbeth, Macduff is the one who reveals that Macbeth killed his family.
Step-by-step explanation:
In Shakespeare's play Macbeth, the person who says that Macbeth has killed Macduff's family is Macduff himself. In Act 4, Scene 3, Macduff learns of his family's slaughter and swears revenge on Macbeth. He later expresses his grief and anger to Malcolm, and together they plan to overthrow Macbeth's tyrannical rule.
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