Starborn

"There was a complex confluence of events, of energies, of circumstances that would have given a child born under them the potential to wield power over Outsiders."

Hints of Something Special
The quote at the beginning of this wiki page was said by Lash during the psychic attack at the end of the battle of the Deeps. This passage seems to be a major hint that there is something special about Harry, and she even says that his Mother had him when she did deliberately.

During the events of Cold Days there were several adversarys that referred to Harry by the enigmatic title of "Starborn" which seems to be a direct reference to the hints dropped by Lash in Winter Knight

Other "Starborn"
The author has stated that Elaine also has the "potential" to wield power over Outsiders: Harry and Elaine are just a few months apart age wise so for all intensive purposes the same age. He then told me that was one of the reasons that Justin had picked both of them to adopt, it wasn't just random kids with power