Who is Alex?

The mystery of Alex Peters is a big one that started in Return to Ghost Town. If you haven't read the book yet, warning: there are MAJOR spoilers ahead.

Okay, so a big reveal halfway through the sequel is that Alex has ferrokinesis (i.e. the ability to move metal with his mind). Not only that but...it also shows that he isn't a true blood member of the Peters family. So...who IS he and how did he get these powers if he ISN'T a part of Jo's family?

I'd love to hear your thoughts about this!