Elon Musk’s Daughter Vivian New York Fashion Week Debut

Exa Dark Sideræl Musk & Techno Mechanicus Musk (Kids)

In her 2022 Vanity Fair interview, Grimes revealed she and Elon privately welcomed a baby girl via surrogacy.

“Exa is a reference to the supercomputing term exaFLOPS (the ability to perform 1 quintillion floating-point operations per second),” she said. “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.'”

Sideræl—pronounced “sigh-deer-ee-el”—is, according to mom, “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.”

Walter Isaacson revealed in his biography Elon Musk that Exa was born in December 2021 via surrogate.

The book also stated that around Father’s Day 2022, the on-again, off-again couple welcomed a child named Techno Mechanicus, nicknamed Tau, also via surrogate. The biography includes a photo, dated June 2022, of Elon feeding the baby boy.

Though Grimes would prefer other salient details be kept private. “I have tried begging the public and my kids dad to keep them offline, and I’ve tried legal recourse,” she shared on social media in 2025. “The state of my children’s lives being public is of grave concern to me and I think about how to solve this every day. It’s insane to me that theres no way to deal with this.”