Reddit mentions of The Royal Descents of 900 Immigrants to the American Colonies, Quebec, or the United States Who Were Themselves Notable or Left Descendants Notable in ... Introduction, and Descent from Ki

Henry VIII most likely has no living descendants, unless you accept the theory that Henry VIII was the father of Mary Boleyn's son Henry Carey.

Assuming you're American, there are genealogical reference works that have lists of the 17th and 18th century American colonists and later immigrants who have traceable and reasonably well-documented royal ancestry: The Royal Descent of 900 Immigrants to the American Colonies, Quebec, or the United States by Gary Boyd Roberts, and Plantagenet Ancestry by Douglas Richardson; these are both reasonably reliable secondary sources. If one of your colonial or later immigrant ancestors is not included then your presumed royal line is probably bogus.