Grimes reveals she and Elon Musk secretly welcomed 2nd baby

Grimes accidentally revealed that she and Elon Musk secretly welcomed a second child together via surrogate.

The singer, 33, spoke about the super surprise new addition — after all, the pair did semi-separate last year — in an interview with Vanity Fair. However, revealing the baby girl's existence didn't seem planned and only became part of the story because the infant kept crying upstairs during the interview after Grimes established that their 1-year-old son, X, was out with his dad.

"I'm not at liberty to speak on these things," Grimes said at first when asked if she had another child. "Whatever is going on with family stuff, I just feel like kids need to stay out of it." She said X "is just out there," referring to the boy she and the Tesla founder call X Æ A-12 and pronounces "X A.I. Archangel" (or X for short). "I mean, I think E is really seeing him as a protégé and bringing him to everything and stuff... X is out there. His situation is like that. But, yeah, I don’t know."

The interviewer asked how it should be handled for the story, pointing out that he just can't pretend he didn't know she has a secret baby with the world's wealthiest man hiding upstairs. They both laughed, leading to Grimes's acknowledgment of the child.

"She's a little colicky too," she said of her daughter, who was born in December.

Grimes (real name: Claire Boucher) calls the baby Y, but, "Her full name is Exa Dark Sideræl Musk."

She explained the meaning behind the name saying Exa is a reference to the supercomputing term exaFLOPS (the ability to perform 1 quintillion floating-point operations per second). Dark is "the unknown. People fear it but truly it’s the absence of photons. Dark matter is the beautiful mystery of our universe." Sideræl — pronounced "sigh-deer-ee-el" — is "a more elven" spelling of sidereal, "the true time of the universe, star time, deep space time, not our relative earth time" and a nod to her favorite Lord of the Rings character, Galadriel.

Grimes said she's prepared for the child to dislike her name.

Of using a surrogate, the performer explained the last month of her pregnancy with X was so difficult she couldn't walk and she "kept collapsing." It was a scary pregnancy and at another point, she thought she was dying. "I hemorrhaged. It was scary," she said.

Grimes and Musk — who has five other sons — wanted more children but she feared serious complications so they turned to a surrogate.

As for Grimes and Musk's relationship status after announcing they had split in September and Musk calling himself "single" in December, "There's no real word for it. 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.”

Grimes, who now lives in Austin but is less than an hour via private jet from Musk's Starbase and a short drive from the Tesla factory, added, "This is the best it's ever been... We just need to be free."

She also said they plan to have more children together, noting, "We've always wanted at least three or four."