Gavin Rossdale Brings Kids Zuma and Apollo On Stage During Show

Gavin Rossdale took his kids on stage during his latest show for some birthday celebrations ... making longtime fans wonder where the hell the time has gone?!?

The Bush frontman brought out 14-year-old Zuma and 8-year-old Apollo at Wednesday night's show at the Hollywood Casino Amphitheater in Chicago ... Zuma's birthday was over the weekend and Gavin wanted the entire crowd to join in the celebration.

The singer called to the wings for 16-year-old Kingston to join them, but the kid was a no-show ... but Zuma still got a huge "Happy Birthday" from the audience, and got to blow out his candles in front of everyone.

Gavin's band is currently on tour with Alice in Chains and Breaking Benjamin -- talk about a rockin' birthday!!!

The little kids ain't so little anymore -- as you know, Zuma, Apollo, and Kingston were the talk of the town growing up ... of course, a lot of that had to do with Gavin's marriage to Gwen Stefani.

Gwen wished her middle child a happy birthday in a sweet Instagram post over the weekend.