I'm a little nutty and I know it
But if you go back and take a look at my history
You will see that I'm not the only one
That's off his rocker, there were many before me

from Eminem – The Apple Lyrics on Rap Genius

Meaning

He’s stating that his craziness is due to his genes. (Though he’s geniusely crazy, most of his relatives were just…mentally ill)

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