Billy Idol has learned he has a long-lost adult son.
The punk rocker made the discovery after his daughter Bonnie was given a DNA test for Christmas, to trace her family history.
"My husband just surprised me with a 23andMe, with a DNA test as a Christmas present," Bonnie, 35, explained in the new documentary about Billy's life, Billy Idol Should Be Dead.
"And then a few weeks later, I get the results back on the app and open it and I'm like, who is this? This Brant. And it says his info's like, New York, 1985, looking for my bio dad. I was like, 'What?'"
While Billy had always known he had two children - Bonnie and her half-brother Willem, 36, none of them had any idea there may be another sibling in the world until they learned of Brant's existence via the DNA test.
Brant had been conceived during Billy's Rebel Yell tour in the 1980s.
"I actually had a son that I didn't realise," Billy told the documentary, who I fathered on the Rebel Yell tour without knowing it".
Brant had also spent his life completely in the dark, having been led to believe someone else was his father until he accessed his family history via the popular DNA test.
"I was like, 'Mom, is there a chance Mark might not be my biological father?' And she's like, 'Well, it's pretty crazy, but back in the day, we broke up and I actually spent a weekend with Billy Idol'," Brant recalled.