In an interview published Thursday by Vanity Fair, Grimes revealed the existence of the baby born in December.
Billionaire entrepreneur Elon Musk and musician Grimes have a second child, a girl they named AXA Dark Sideril Musk - though parents mostly call her Y.
Grimes, 33, revealed the existence of the baby born in December in an interview published Thursday by Vanity Fair.
And she did it by mistake, it seems: The magazine reporter said she heard what sounded like a baby crying during the interview at Grimes' home in Texas and after Grimes won and acted clearly, She finally confirmed that, yes, she was a mother again.
Due to fear that she would have complications, which Grimes said she endured during her first pregnancy, the parents decided to use a surrogate this time.
The birth of their first child, a boy born in May 2020, was closely watched in the press – especially because of the choice of name: X A-12, or more simply, X.
Elon Musk - the head of Tesla and SpaceX, and currently the world's richest man - announced last fall that he was "quasi-separating" from the singer.
"I would probably refer to him as my boyfriend, but we're very fluid," Grimes told Vanity Fair.
The eclectic artist, whose real name is Claire Boucher, said she and Musk live in separate homes but remain "best friends."
"We see each other all the time ... we're just having our say, and I don't expect other people to understand that," she said.
Grimes said she and Musk plan to have more children: "We always want at least three or four," she said.
The name AXA Dark Siderail, Grimes explained, includes several references to space and technology: He said AXA refers to supercomputing; Sideræl, a more "elven" spelling of Siderl - this word means to include distant stars - and Dark, for "the unknown".
"Dark matter is the beautiful mystery of our universe," said Grimes, who didn't rule out that her daughter would like to change her name in the future.
Grimes also said that she hopes to keep her daughter out of the public spotlight.
"The best situation here is that I'm training the girl and he's training the boy," she told Vanity Fair at her home in Austin, Texas.
After recently selling all of his Los Angeles real estate, Musk has said that his main residence is now in southern Texas at SpaceX's rocket manufacturing and launch site.
In November, the blond-headed X could be seen sitting on his father's lap during a virtual presentation on the space company's new rocket.
Musk, 50, has been divorced three times and has eight children, including a toddler who died at just 10 weeks old.