I've quoted the headline of this Discovery article above as it's surely an early contender for history news title of the year. Basically, an Italian family have had in their possession an elaborately decorated squash which is used to house a handkerchief which, according to family legend, was dipped in the blood of the executed King Louis XVI during the French Revolution.
Now, we know that when Louis died people did come forward to try and take a sample, so this isn't entirely ridiculous, but until now there's been no way of proving where the blood really came from. However, DNA from the blood has been compared to the DNA of a head, which is claimed to be the that of French King Henri IV. As this head is also a relic of the anti-religious movements of the French Revolution (it was allegedly taken from its crypt, abused a bit, then saved), no one knew if it was really from the king. What's happened is the DNA from the blood has been compared with the DNA from the head... and discovered there's a really good chance the two were related down the paternal line, which does increase the chance both are from the two kings.