There's another baby on board for Grimes and Elon Musk (no SpaceX needed).
In a new interview with Vanity Fair, published March 10, the 33-year-old musician revealed that she and the Tesla CEO, 50, privately welcomed a baby girl recently via surrogacy. During the in-person sit-down, the journalist noted that their second child spilled the beans themselves accidentally when she was heard crying from another room.
As Grimes already confirmed beforehand, the pair's 22-month-old son, XA-12 Musk also known as "Baby X" was not home at the time. As for their baby girl's name, she falls right in line with her brother since Grimes also revealed she goes by the letter "Y." "Her full name is Exa Dark Siderl Musk," Grimes told the Vanity Fair reporter through text messages. "Exa is a reference to the supercomputing term exaFLOPS (the ability to perform 1 quintillion floating-point operations per second). Dark, meanwhile, is 'the unknown. People fear it but truly it's the absence of photons. Dark matter is the beautiful mystery of our universe.'"
As for Siderl -- pronounced "sigh-deer-ee-el" -- Grimes noted it's "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, who "chooses to abdicate the ring."
Get top local stories in Philly delivered to you every morning. Sign up for NBC Philadelphia's News Headlines newsletter.
Last fall, Musk -- who is also a father to five sons from a previous relationship --confirmed that he and Grimes split after three years of dating.
"We are semi-separated but still love each other, see each other frequently and are on great terms," Musk told Page Six in September. "It's mostly that my work at SpaceX and Tesla requires me to be primarily in Texas or traveling overseas and her work is primarily in LA. She's staying with me now and Baby X is in the adjacent room."
And if you're wondering where the two stand now amid the latest addition, Grimes told Vanity Fair that they're simply "happy." "There's no real word for it," she shared of their relationship. "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... This is the best it's ever been... We just need to be free." And it's worth noting that there may be more children in the future for the pair, as Grimes also revealed that she and Musk have "always wanted at least three or four."