Mathematically, it is plausible that all the "well-known" ( not that well actually) people of ancient times who had enough children, or the people of the northern sagas (a saga does not mean the same thing as a fairy tale), are several times ancestors of a common Europeans and descendants of Europeans. The fact is, however, that many Kingdoms and nobles bought themselves lineages that lead to the Bible. Personally, I believe in some of these oldest lines more than others :) I have learned that it is sooo difficult to find evidence and sources. (The ancient DNA study is interesting, of course we do not know through what lines the kinship comes from)