Complex sentence: It may have been related to the "Coahuiltecan", but researchers cannot be certain as so little is known of languages in this region, and there was not "one single"'Coahuiltecan' language.
Split into simpler sentences: It may have been related to the "Coahuiltecan". Researchers cannot be certain as so little is known of languages in this region, and there was not a single'Coahuiltecan' language.