The singer - already a father to three-year-old son James Hoke - has announced he and his wife Leigh will welcome a second boy into the world early next year.
Howie - who celebrated his 39th birthday yesterday (23.08.12) - tweeted on Monday (21.08.12): ''Thanks to family, friends & fans for all the amazing birthday wishes. This year I'm receiving the best gift from my wife: another baby boy!
''I know it's not until Wed, but I already feel like I am having an incredible bday with the baby boy news and all of the amazing bday wishes! (sic)''
Howie's bandmate Aj Mclean recently announced his wife, Rochelle Karidis, was expecting a baby girl.
He wrote on twitter: ''Baby announcement coming soon!''
He later revealed to his hundreds of thousands of followers: ''Yay we're having a baby girl!!!!! Little baby Ava Jaymes.''
The 34-year-old singer also posted a video message to his fans on SocialCam.
He said: ''Thank you guys for all of your love and support. This will be the first Backstreet girl.''