هَذَا أَبُوكَ
This is your father.
The sentence may be addressed to someone who knows his father but neglects the obligations attached to that relationship. On the surface the information is redundant; rhetorically it serves as an admonition arising from an acknowledged fact.
The informed person is treated as if unaware because their conduct fails to reflect what they know. The shift concerns rhetorical treatment, not an actual absence of knowledge.