Though Jenner's older siblings are usually the ones making headlines, the 14-year-old stole the spotlight Sunday when she and Simpson 14, stepped out for a date at The Grove shopping mall in Los Angeles.
The pair met last week at The Twilight Saga: Breaking Dawn - Part 1 premiere and "have been inseparable since," a source told the celebrity magazine. "They are a couple! They are so cute together," the source added.
Dubbed the Justin Bieber of Australia, Simpson was discovered playing covers of Jason Mraz and Justin Timberlake on YouTube in 2009. The teenager from Australia's Gold Coast has since moved to the US and his Coast To Coast EP was released in September, debuting at number 12 on the Billboard 200.
Bieber's manager, Scooter Braun, has signed Simpson to a worldwide management deal and fans are hoping a Simpson/Bieber duet could be coming soon. Jenner meanwhile has made a name for herself on her family's E! reality show and has dabbled in modeling for Sears and Teen Vogue.