Billy Idol wasn't surprised to discover that he had fathered a child during the 1980s

In an interview with The i newspaper, Billy said: "Maybe a little bit, but the more I thought about it, I guessed there must be something like that, because we were going around in the 80s, and 70s, just having knockdown, drag-out sex with a million people you didn't know. A lot of people in the rock world got children beyond their usual relationships."

Idol has forged a close bond with Brant - who lives in New York and works in the construction trade like his father and uncle did.

The 69-year-old rocker said: "We're quite good friends, and I love him. He's a nice guy."

Billy recounts in the documentary Billy Idol Should Be Dead - which premiered at the Tribeca Festival earlier this month - how he almost died from a heroin overdose and was relieved that he cheated death so he could enjoy the success of his 1983 album Rebel Yell, which reached the top 10 in the US Billboard charts.

The Eyes Without a Face singer said: "I'm just glad I didn't die, because I had this great album and I wanted to come back to England and say - 'Now what do you think?' I nearly blew that. So I'm glad I lived through it."

Idol, whose real name is William Broad, struggled with drug addiction during his time in the spotlight and admits that his problems were worsened by the fame that came with music success.

He explained: "You start being known by the general public who don't necessarily give a s*** about your music. They just know that spiky blonde hair and go, 'Hey it's Billy!'

"That's where the pressure came in, as gradually your world closed down. You're stuck in tiny rooms trying to expand your life beyond that. You might as well be as high as a kite doing that."

Billy will celebrate his 70th birthday in November and is now happy to be a doting father and grandfather after overcoming his addiction issues.

He said: "I'm all set up for that. I'm in a better place in my life. In lots of ways, I've done everything I wanted, at least to my own satisfaction. And now I'm not a drug addict, I can really be there for them."