Jonas Brothers Celebrate Nick's 21st Birthday at XS!

Nick Jonas wraps his arms around his girlfriend Olivia Culpo while arriving at the XS nightclub inside the Wynn Las Vegas Resort on Sunday (September 15) in Las Vegas.

The singer was joined by his brother Joe, his girlfriend Blanda Eggenschwiler, as well as Kevin and his pregnant wife Danielle as they celebrated Nick‘s 21st birthday – Happy Birthday Nick!

PHOTOS: Check out the latest pics of Jonas Brothers

“Happy 21st to one of my best friends and a great brother @nickjonas,” Joe wrote on his Twitter account.

20+ pictures inside of the Jonas Brothers and more at XS nightclub…