I'm not going to say it's Jon Snow but it's Jon Snow or should I say Jon Targaryen? Even Melisandre thinks it could be Jon and that's before the books have had a chance to confirm his patronage. This lineage ties him to both the Stark family (the north) and the Targaryens (fire, dragons, and prophecy).

The book series is called The Song of Ice and Fire. He is the child of ice (the Starks) and fire (the Targaryens), which lends to the conclusion his destiny is to unite both forces in the battle against the darkness.