The whole idea that Shiwan is the last relative of Genghis Khan is pretty funny, because Genghis Khan actually has one of the biggest lineages in the world. 0.5% in the world are related to him. That's 16 million people. So Shiwan isn't special at all.
http://blogs.discovermagazine.com/gnxp/2010/08/1-in-200-men-direct-descendants-of-genghis-khan/#.V5TlJuhCRSA