Grimes Announces Birth of Second Child With Elon Musk Via Surrogate

The singer also reveals her daughter's unique name.

Grimes has welcomed her second child with Elon Musk. The 33-year-old musician, whose real name is Claire Elise Boucher, shared the news in a new Vanity Fair cover story. 

During the interview, Grimes is hesitant at first to discuss expanding her family, saying, "I’m not at liberty to speak on these things. Whatever is going on with family stuff, I just feel like kids need to stay out of it, and X is just out there." 

However, she then shares that she and Musk, 50, secretly welcomed a daughter they call Y via surrogate in December. 

“Her full name is Exa Dark Sideræl Musk," Grimes tells the magazine. 

As for the meaning behind the unique moniker, Grimes shares that Exa is a reference to the supercomputing term exaFLOPS (the ability to perform 1 quintillion floating-point operations per second), while Dark represents "the unknown."

"People fear it but truly it’s the absence of photons," Grimes says. "Dark matter is the beautiful mystery of our universe.” 

As for Sideræl -- pronounced sigh-deer-ee-el -- Grimes describes it as "a more elven" spelling of "sidereal," which means “the true time of the universe, star time, deep space time, not our relative earth time.” It’s also a nod to Grimes' favorite Lord of the Rings character, Galadriel. 

Steven Klein/Vanity Fair

Despite welcoming a second child together, Grimes remains vague about her on-off romantic status with Musk. 

"There’s no real word for it,” she says. “I would probably refer to him as my boyfriend, but we’re very fluid. We live in separate houses. We’re best friends. We see each other all the time… We just have our own thing going on, and I don’t expect other people to understand it.”

She adds that their relationship is "the best it's ever been," saying they plan to have more children in the future. 

"We've always wanted at least three or four," she says. 

As for their first child, Grimes says Musk has high hopes for the almost 2-year-old. 

"I think E is really seeing him as a protégé and bringing him to everything and stuff.… X is out there," she says. "His situation is like that."