Curious phenomenon where there's only one true descendant of the some legendary hero/villain or chosen one. Usually it's only that one person who can save the day or bring about The End of the World as We Know It. Because Destiny Says So, of course. And often it has to be the male line, or whichever keeps the last name. The fact that there's multiple branching into different last names doesn't count genetically for some bizarre reason. Note that, in the present generation, if there is another sibling, he or she tends to be recruited by the Big Bad as the Evil Counterpart.