yehohuaahron, citing a list of family names that are descended from Dovid Hamelech means nothing. First, because in many cases it is an unproven claim. Second, because many people with those family names are descended through females. Take the lubavicher rebbe, for example. He is ben achar ben from the Tzemach Tzedek whose father was an Altshuler. Yet his family name was Shneerson. So family names don’t prove a lot.
You will also find, unfortunately, that there are goyim with those family names as well, as they are descended patrilineally from those families. I have a friend who was in business in the States with a goy whose family name was… Shneerson. Rachmono litzlon!