Elon Musk and Grimes Welcome Second Baby Together, Daughter Exa Dark Sideræl

Grimes is a mom of two!

The singer, 33, secretly welcomed another baby with Elon Musk, she revealed to Vanity Fair in a cover story for the magazine's April 2022 issue.

Grimes — who is also mom to 22-month-old son X Æ A-12, whom she also shares with the Tesla founder, 50 — told Vanity Fair that she and Musk welcomed a daughter in December 2021 via surrogate.

The baby's full name is Exa Dark Sideræl, though they've nicknamed her Y, according to Vanity Fair.

Grimes explained her daughter's unique name to the outlet, telling Vanity Fair that Exa refers to a supercomputing term, exaFLOPS, while Dark represents "the unknown." She explained, "People fear it but truly it's the absence of photons. Dark matter is the beautiful mystery of our universe."

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Sideræl, the third part of Y's full name, is pronounced "sigh-deer-ee-el," according to Vanity Fair. Grimes called the word "a more elven" spelling of sidereal, which she defined as "the true time of the universe, star time, deep space time, not our relative earth time."

Sideræl has a double meaning, too, as a shoutout to Grimes' favorite Lord of the Rings character, Galadriel, who "chooses to abdicate the ring."

Grimes told Vanity Fair that she was "fighting" to name her daughter Odysseus Musk, because "A girl named Odysseus is my dream," but she and Musk settled on Exa Dark Sideræl instead.

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Despite splitting up in September 2021 after three years together, Grimes told Vanity Fair that she and Musk are back together.

"There's no real word for it," she said. "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."

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She added that she and Musk are happy together, telling the outlet, "This is the best it's ever been. ... We just need to be free."

She told the outlet that they plan to have more children too: "We've always wanted at least three or four."