Dave Grohl hired a divorce attorney before announcing he recently had a child outside of his 21-year marriage, a source tells PEOPLE.

A spokesperson for Grohl did not immediately respond to PEOPLE’s request for comment.

Grohl, 55, has been married to his wife Jordyn Blum, 48, since 2003 and they have three daughters: Violet, 18, Harper, 15, and Ophelia, 10.

The Foo Fighters frontman revealed in an Instagram post on Tuesday, September 10, that he has had a daughter with another woman, whose name he did not know.

“I recently became the father of a new baby daughter, born out of wedlock,” Grohl wrote in a statement. “I plan to be a loving and supportive parent to her. I love my wife and my children, and I am committed to earning their trust and forgiveness. We are grateful for your consideration for all of the children involved as we move forward together.”

News reports that Grohl and Blum’s eldest daughter has deactivated her Instagram account: It’s unclear when Violet, who previously performed with her father, closed the account, but it was still inactive as of Wednesday morning.

Grohl and Blum first met in 2001, when she was working as a producer at MTV, Spiders reported. The couple married on August 2, 2003, in a wedding attended by celebrity friends, including legendary music executive Clive Davis and Grohl’s former Nirvana bandmate Krist Novoselic.

In 2003, Grohl said Teenage people Blum was “just about” the first person he had been truly honest with. “Now I have nothing to hide,” he said. “If you’re not trying to be someone else, being honest is easy.”

That same year, Grohl told PEOPLE that he rekindled their relationship after his now-deceased bandmate Taylor Hawkins’ 2001 painkiller overdose gave him a new perspective on life.

“I had decided I didn’t want a serious relationship because I was single and I was running around — I was free,” he said at the time. “But that was the first thing I thought about when Taylor woke up from (his coma): I had met the woman I was going to marry and have kids with and I hadn’t spoken to her in months. She said, ‘You’re the last person I thought I would ever hear from again.’ And I said, ‘Hey, let’s go out to dinner.'”

After saying “I do,” the two became not only spouses but collaborators. Blum — who previously co-directed the Foo Fighters’ 2002 “Walk a Line” music video — appeared in the band’s 2011 “White Limo” video. Blum has also been a muse for Grohl, who said she inspired songs like “Statues” and “Burn Away.”

The duo were last spotted together in London, when they took part in Wimbledon in July.