It's a great-great-uncle but he was claiming someone who was a direct ancestor to Elizabeth Warren. It's just that it is still doubtful whether that ancestor really had Indian ancestry--and generally someone who is only 1/32 or 1/64 Native American isn't recognized as being Native American and entitled to the affirmative action benefits attached to that status.
It appears more likely that Warren is descended from one of the white men who helped round up the Cherokees for the Trail of Tears.