No Doubt singer Gwen, 44, gave birth to a baby boy on Friday and Gavin confirmed the newborn's quirky name the following day.
"@gwenstefani welcome APOLLO BOWIE FLYNN ROSSDALE ❤️❤️❤️ 2/28/14 ❤️❤️❤️," tweeted proud new father Gavin. "Bowie and Flynn = [our] mothers' maiden names."
Gavin's Twitter message was promptly retweeted by Cool singer Gwen as well as over 700 of the couple's fans.
Baby Apollo is younger brother to Gwen and Gavin's sons Kingston James McGregor, seven, and five-year-old Zuma Nesta Rock, as well being half-brother to Gavin's daughter, British model Daisy Lowe.
California-born Gwen kept a low profile throughout her pregnancy.
While reports emerged that she was several months pregnant at the end of August, Gwen didn't confirm the exciting news until late October.
Expectant stylist Rachel Zoe put an end to speculation by posting a picture of herself and Gwen showing off their baby bumps at the Beverly Hills' Wallis Annenberg Center for the Performing Arts Inaugural Gala.
Three months later Gwen revealed that she was expecting another boy.
"Was ready to hand over the crown," she tweeted. "But I guess I am still queen of the house. #itsaboy #surroundedbyboys."
With less than a month to go until her due date, Gwen hosted a star-studded baby shower which was attended by numerous celebrities including Gwyneth Paltrow, Jessica Alba and Nicole Richie.