Simpson was born to Brad and Angie Simpson. He has two younger siblings, Tom and Alli. He is also a talented swimmer, winning two gold medals at the Queensland Swimming Championships. Simpson trained at the Miami Swimming Club under coach Ken Nixon.Simpson's mother Angie works as a volunteer at the club.

Simpson began to record songs in his bedroom during the summer of 2009 on YouTube, performing "I'm Yours" by Jason Mraz, "Cry Me a River" and "Señorita" by Justin Timberlake, "I Want You Back" by the Jackson 5, and his own songs, "One" and "Perfect." He was subsequently discovered on YouTube by Shawn Campbell, a Grammy-nominated record producer who has produced for Jay-Z and other artists.