Kamandi

Kamandi, the Last Boy, was the last boy to exist in the timeline.

Biography
Kamandi was the last boy in the timeline of Earth-1. As of 2049 Eobard Thawne had recorded the entire timeline from Anthro, the first boy, to him.

Behind the Scenes

 * In the comics Kamandi is the last boy on Earth. He lived in a post-apocalyptic world dominated by animals.