Kevin Richardson is Backstreet's Back, all right. The fifth member of the Backstreet Boys has announced that he is formally rejoining the group after leaving in June 2006.

In footage posted on their website from their show with New Kids on the Block at London's O2 Arena, BSB member Nick Carter told the excited room, "I think we should let them in on the secret we have. Since we love you guys so much, especially in London, that we are going to come back, we are going to be back in July to record the next Backstreet Boys album this year."

While that bit of news had the crowd cheering, it was what Brian Littrell shared that really got the room screaming. "There's two parts to that secret," he said. "And Kevin is coming back!" They then added that they might play shows with all 10 members of NKOTBSB.

Though Richardson left the group six years ago, he has made sporadic concert appearances with the band, including one on the Backstreet Boys cruise back in December. Still, the remaining members of the band always were skeptical that a full-fledged reunion would ever take place.

On Twitter, they had this additional message for their fans. "Now everything is back to normal ... Welcome back @kevinrichardson." For his part, Kevin seemed pretty stoked about being reunited with his band of brothers, adding on his Twitter, "Hello beau-ti-ful people. Yes, the cat is OFFICIALLY out of the bag. It's on and crackin!"

Richardson's return wasn't the only big news the guys of BSB had for fans. A.J. McLean posted a video message revealing that he and his wife, Rochelle, are expecting their first child together. "Because we love you all so much, we wanted to share with you for the first time something very special: We're having a baby!" the couple said in the video message. "See you guys soon."

Voting in round two of MTV's Battle of the Boy Bands runs until noon ET on Monday, April 30. Winners are determined by fan votes, so if your favorite band made the cut, make sure you keep voting. Tune in to AMTV and MTV Hits for their boy-band video takeovers each day and make sure to spread the word on Twitter using the hashtag #BBB and like us on Facebook for updates!