Nothing can make you more proud as a father than to see your child succeed at what they want to do. Billie Joe Armstrong's son decided to follow in his father's footsteps and join a punk rock band called SWMRS.
A video on YouTube from a couple of years back shows shows the band, with Billie Joe's son Joey on drums, performing live to a smaller crowd. At around the 1:30 mark on the video, the camera cuts to the crowd, showing Billie Joe moshing with the crowd and looking like he is the happiest man on the planet.