EXCLUSIVE: A.J. McLean Reveals the Sex of Baby No. 2!

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A.J. McLean is having another girl!

The Backstreet Boys singer exclusively revealed the happy news to ET’s Deidre Behar at the premiere of music documentary We Are X in Los Angeles on Monday night.

“A lot of girls in the house!” McLean said with a laugh. “I will take that over testosterone running around the house, to be honest with you.”

“All my boys have boys, so it's nice to have girls,” he added. “Girl power all the way!”

RELATED: Backstreet Boy AJ McLean and Wife Rochelle Expecting Baby No. 2!

The singer and his wife, Rochelle, are already parents to a 3-year-old daughter, Ava, and McLean told ET that his little girl is “ecstatic” to be a big sister.

“She has her own little baby that she's been tucking under her shirt like she's pregnant!” he gushed. “She's like, swaddling her babies now… She loves it, she's so sweet and she's just an awesome kid.”

McLean revealed that his wife is due “literally just shy of a week after” the Backstreet Boys’ first run of their new Larger Than Life residency at Planet Hollywood's The Axis Theater in Las Vegas.

“Hopefully I'm not in the middle of the show and all like, 'I have to go!'” he laughed.

Rochelle later took to Twitter to jokingly chastise her husband for revealing the sex of their baby, apparently without discussing it with her first.

"When your husband announces the sex of your baby but forgets to tell you and you find out on Twitter! Lol," she tweeted Monday night, adding the hashtag, "#babygirlnumber2."

NEWS: Backstreet Boys Finally Announce Las Vegas Residency for 2017

McLean also teased the 2017 residency shows, revealing that the performances will feature a little something for all Backstreet fans.

“If you've ever been to our Millennium concert or the Black and Blue concert, put those two concerts together and multiply it by 100,” McLean explained. “Add a little bit of glitz, and a little bit of glamour -- that'll be Vegas.”

Check out the singer’s mixed feelings about his kids listening to his music in the video below.

EXCLUSIVE: A.J. McLean Has Mixed Feelings About His 3-Year-Old Daughter Loving His Music