Jason Merritt/Getty Images for Wallis Annenberg Center for the Performing Arts
"Welcome Apollo Bowie Flynn Rossdale 2/28/14," Rossdale tweeted on Saturday, confirming the bundle of joy arrived on Friday. He added, "Bowie and Flynn = mothers' maiden names."
Apollo joins big brothers Kingston, 7, and Zuma, 5. The Bush frontman is also dad to model Daisy Lowe, 24, from a prior relationship.
"I was ready to hand over the crown. but I guess I am still queen of the house. #itsaboy #surroundedbyboys," the three-time Grammy winner, 44, wrote in the accompanying caption.