In order to help more details are needed.
Who is the relative (male) his full name, parentage, children, where did he live,timeframe etc., who purportedly married a Cherokee Indian???. Also her first name if you have one...
. If he did marry a native American the term marriage does not always mean a civil or church ceremony. The Indians and others would have had a difficulty marrying because of interracial issues in many of the states so they performed a ceremony called it "jumping over the broom" or some other form of a marriage ceremony. Also many lived as common law couples... so there might not be any written records available .