He wasn't even that. Ever heard of the Star Spangled Kid? The golden age version was a teenage hero with an adult sidekick, Stripesy. They were on the Seven Soldiers of Victory team, but did also have solo adventures in the golden age. They ended up time displaced, Star Spangled Kid became the leader of 1980s team Infinity Inc as Skyman before dying, while Stripesy became the stepfather of the second Star Spangled Kid in the 1990s, who later became Stargirl.
Peter's only the first teen superhero to not be a sidekick or younger version of an established hero and have his own book. Supergirl's older but didn't have her own comic yet in 1962.