The original Aqualad that started the Aquaman and Aqualad team up was, Garth. The team up was created by Robert Bernstein and Ramona Fradon. This sidekick and superhero team up was very much inspired by other sidekick teams Batman/Robin, Green Arrow/Speedy, and The Flash/Kid Flash. Sidekicks were suppose to attract younger readers by giving the young reader a character to relate too.
The Original Aquaman and Aqualad
After being set out to die to due to being deemed genetically inferior by the Atlanteans, young Garth was rescued by Aquaman and became his young sidekick, Aqualad. Together the team had plenty of adventures, but once Aquaman got married to Mera and had a kid of his own the adventuring became less important and by Aqualad feel unsure of his role in life.