There was a boy band summit in Sin City this weekend -- as New Kids on the Block, Backstreet Boys and 98 Degrees all partied in Vegas!

Nick Lachey kicked things off by celebrating his bachelor party Friday night at TAO at The Venetian, where he was joined by his brother Drew and a large group of guys. The partying continued the next day at TAO Beach, where Nick hit the pool with former band mates Drew, Jeff Timmons and Justin Jeffre.

Nick and Co. weren't the only 90s boy banders in Vegas though, as the Backstreet Boys and New Kids on the Block (collectively known as KNOTBSB) went to Paris Las Vegas after their concert in the city on Sunday.

The super-group was seen grabbing some candy at the Sugar Factory before heading to Gallery, where Nick Carter, Howie Dorough and Donnie Wahlberg all hit the stage to hype up the crowd.

Can we get Nsync back together already?