Kevin Federline has sparked reports he's back with his ex-girlfriend Shar Jackson after taking her to Las Vegas for a birthday weekend.

Federline split from Jackson, the mother of two of the rapper/dancer's kids, to romance ex-wife Spears. But now it looks as if the former lovers are an item again.

Federline and Jackson were spotted enjoying each other's company on Friday afternoon in a private cabana at Tao Beach, before partying at Sin City's Prive nightclub on Friday night.

According to Hollyscoop.com, "Federline even went to the club's DJ booth to publicly wish Shar a happy birthday".

A source says, "Shar joined Kevin in the DJ booth, where he proceeded to sing along on the microphone to Put On by Young Jeezy and Welcome to Jamrock by Damien Marley."