Noah Maxwell is the main character of Tribe Twelve.
Milo Asher was Noah's cousin and best friend. However, Milo wasn't an ordinary kid. He had a bad case of paranoia, and had sleeping pills. He overdosed on his sleeping pills shortly after hanging out with Noah for the last time, during witch he showcased his mental problems. Given everything that has happened to Noah, he believes that Milo met his end not though sleeping pills, but prehaps worse. Milo had a journal that he kept with him that may contain information about the things he was going though without Noah.
According to Mary Asher, Milo's mother, Milo had been deeper involved in this case as it is suggested that the Collective have been keeping a close eye on Milo and Mary for a number of years, and simply moved on to Noah after Milo died.
Also, Noah's Youtube account, TribeTwelve became a memorial page for Milo after his Tribetwelve project got cancelled. When Noah began investigating the footage, he did see more of Milo's paranoia taking effect, which he doesn't recall. Its around this time the Observer starts getting into his life.