Haida was formerly grouped with Na-Dene, but linguists such as Lyle Campbell consider the comparative evidence for that link inconclusive and classify Haida as a language isolate instead. A separate, still-debated hypothesis (Dene-Yeniseian) proposes linking Na-Dene itself to the Yeniseian languages of Siberia, the only living member of which is Ket.
What would resolve this A body of regular sound correspondences and shared basic morphology between Haida and the Athabaskan-Eyak-Tlingit core of Na-Dene, of the kind the comparative method requires, rather than the more impressionistic lexical resemblances the original grouping rested on.
OpenHistorical and comparative linguisticsWikipedia: Na-Dene Languages