Boy, Kevin Federline sure seems like a relic from a distant past. His ex-wife Britney Spears is now engaged to marry her boyfriend and former manager Jason Trawick, who proposed last night on his 40th birthday, Us Weekly reports.The couple, who first met in 2006, plans to celebrate their engagement at Planet Hollywood in Las Vegas.

With her blowout Femme Fatale world tour under wraps, Spears, 30, and Trawick recently moved into 10,000 square-foot manions outside Los Angeles, along with Spears' two kids — Sean Preston, 6, and Jayden, 5. "OMG. Last night Jason surprised me with the one gift I've been waiting for. Can't wait to show you! SO SO SO excited!!!!" Spears, 30, tweeted Friday morning, hinting at the big news.

This will mean wedding number three for Spears, who was previously married to Federline, 33, her boys' father. In 2004, she wed longtime pal Jason Alexander in Las Vegas, but the marriage was annulled within 55 hours.

Watch Trawick and Spears together in the "Criminal" video here: