Last remaining descendant of Tibetan kings graduates from St. Andrew's (Warning: you can only access this article a few times before you will be asked to pay to view it again. It is paraphrased in this Daily Mail article.)
I was surprised to see the Daily Mail referring to this young man, Namgyal Wangchuk Lhagyari Trichen, as the "last king of Tibet," so I went searching for more information. There are few online references to him in English. His names are not always listed in the same order, which makes searches more difficult.
The Dalai Lama is said to have participated in a coronation ceremony for this young man, but I can't find any reference to him on the Dalai Lama's official website. Nor is he mentioned on the Central Tibetan Administration site, although his father is mentioned as a past member of the government-in-exile's parliament. One of the best sources I found was this article about the young man's sister Namgyal Dolkar.
In short, this young man is recognized as a descendant of royalty, but it does not seem his family has actually ruled Tibet in the past thousand years, as this About.com guide points out. Calling him THE king of Tibet gives a false impression. It is probably more accurate to call him a religious king. Here is what Wikipedia has to say about his ancestor Songtsän Gampo, founder of the Tibetan empire and "the first of the three Dharma Kings… who established Buddhism in Tibet."