The family that plays together, stays together -- and in the case of No Doubt's Gwen Stefani and Gavin Rossdale of Bush, that means occasionally popping up onstage for surprise duet renditions of your dearly beloved's greatest hits.

Stefani proved it on Saturday (Dec. 8) by making an appearance during Bush's set at KROQ's Almost Acoustic Christmas show, joining her hubby for a performance of 'Glycerine' that provided a nice extra musical treat for the crowd. It was also a sweet testament to the couple's relationship, which -- as Aceshowbiz pointed out in its report on the show -- started at an Almost Acoustic Christmas show 17 years ago.

It's been a year full of music for the Stefani/Rossdale clan -- what with Rossdale promoting Bush's 2011 reunion record 'The Sea of Memories' and Stefani tied up with the new No Doubt album, 'Push and Shove' -- so it's nice to see that even in the midst of all their various obligations, one of alt-rock's longest-running power couples can still find the time to make a little music together. Have a look at the video, embedded below.

Watch Bush perform 'Glycerine' with Gwen Stefani