Will Sage Astor-Elon Musk and Grimes Have a Third Child, New Biography Says

Elon Musk and Grimes share three children,Will Sage Astor not two as previously believed, according to a new biography about the Tesla CEO.

In addition to being parents to son X Æ A-12, 3, and daughter Exa Dark Sideræl, 20 months, the on-again, off-again couple at one point welcomed a child named Techno Mechanicus, nicknamed Tau, the New York Times noted in a Sept. 9 review of Walter Isaacson's book Elon Musk, set to be released Sept. 12.

E! News has reached out to Musk and Grimes' reps for comment and has not heard back.

The SpaceX CEO, 52 and now a father of 11, and the musician, 35, have dated on and off since 2018 and welcomed their daughter, nicknamed Y, via surrogate. Grimes had revealed her existence in a 2022 Vanity Fair interview, adding that she and Musk have "always wanted at least three or four" children.

Grimes also told the magazine that the two were living in separate houses and were "best friends." She later tweeted, "Me and E have broken up *again* since the writing of this article haha, but he's my best friend and the love of my life, and my life and art are forever dedicated to The Mission now."

Musk also shares 19-month-old twins Strider and Azure with Shivon Zilis, an executive at Neuralink, one of the companies he co-founded. Their names were first revealed publicly in a Sept. 6 Time magazine cover story adapted from Isaacson's upcoming biography.

"He really wants smart people to have kids," Zilis is quoted as saying about Musk, who offered to be her sperm donor so that, Isaacson adds, "the kids would be genetically his," according to the recent New York Times review of the book.

Before starting a family with Grimes and Zilis, Musk previously welcomed six children, including twins, with ex-wife Justine Musk.

See Musk's complicated family tree below:

Maye was born in Saskatchewan, Canada and emigrated with her parents to Pretoria, South Africa in 1950, when she was 7. She and Elon's father, Errol, split in 1979.

After Elon moved to Canada at age 17, Maye obtained Canadian citizenship by birthright and moved there too, as did his siblings.  There, she established a dietician practice and became President of the Consulting Dieticians of Canada, per Forbes. She also worked as a model.

In 2019, after Elon sold his company Zip2 to Compaq for more than $300 million, he bought his mom an apartment in New York City, where she lived for 13 years and continued her modeling career. She is signed to the IMG Models agency. 

"I brought my children up like my parents brought us up when we were young: to be independent, kind, honest, considerate and polite," Maye wrote in her essay. "I taught them the importance of working hard and doing good things."

Elon's father is an engineer and like Elon, was born in South Africa. In the 2015 biography Elon Musk: Tesla, SpaceX and the Quest for a Fantastic Future, author Ashlee Vance wrote that Elon and his dad had a difficult relationship. In an emotional 2017 Rolling Stone interview, Elon criticized his father and talked about his upbringing, saying that after his parents split, he moved in with his dad, which, he said, "was not a good idea."

Errol told Rolling Stone, "I love my children and would readily do whatever for them."

In a 2015 Forbes interview, Elon's dad said he used to take his kids on trips overseas. "Their mother and I split up when they were quite young and the kids stayed with me," he said. "I took them all over the world."

After divorcing Elon's mother Maye, Errol married Heide, mother of Jana Bezuidenhout, who was 4 years old at the time. Errol and Heidi went on to have two daughters together before they too broke up. In 2017, Errol and Jana had a baby together, son Elliot. They welcomed a second child, a daughter, in 2019.

Kimbal, born in 1972, is a restauranteur. He is the founder of The Kitchen, a collective of 5 restaurants that source directly from local farmers, Forbes reported in 2018. He also runs a non-profit, Big-Green, that has built 200 learning gardens in schools across the U.S., the outlet said.

Tosca, born in 1974, is a filmmaker. In 2017, she founded Passionflix, a female-focused streaming service that targets the billion-dollar romance novel industry, according to Forbes.

Elon and Canadian-born Justine, his college sweetheart from Queen's University in Ontario, married in 2000.  In a 2010 article she penned for Marie Claire, titled I Was a Starter Wife: Inside America's Messiest Divorce, Justine said that while dancing at their wedding reception, Elon told her, "I am the alpha in this marriage."

"I shrugged it off," Wilson wrote, "just as I would later shrug off signing the postnuptial agreement, but as time went on, I learned that he was serious."

The two welcomed their first child, son Nevada Alexander, in 2002. The baby died at age 10 weeks from Sudden Infant Death Syndrome (SIDS). "Nevada went down for a nap, placed on his back as always, and stopped breathing," Justine wrote in her article.

The couple pursued IVF to conceive again went on to welcome five more boys—twins and triplets.

In 2008, Elon filed for divorce. They share custody of their sons and daughter.

Elon appears with his four eldest sons, including his triplets, and Pope Francis on July 1, 2022.

Elon and Justine welcomed their twins in 2004. In 2022, Elon's daughter filed a petition to change her full name in accordance with her new gender identity, writing, "I no longer live with or wish to be related to my biological father in any way, shape or form."

Elon and Justine welcomed their triplets in 2006. 

Elon and Tallulah, who played host greeter Angela on HBO's Westworld, married in 2010.  "It all happened very fast," she told CBS News. "We were engaged after, I think, two weeks of knowing each other." 

The two divorced in 2012, remarried a year later before the pair divorced again in 2016.

Elon and Amber went public with their romance in early 2017, a year after she filed for divorce from Johnny Depp and Elon and second wife Tallulah Riley divorced for the second time. Months later, Elon and Amber called it quits. 

"I just broke up with my girlfriend," Elon told Rolling Stone. "I was really in love, and it hurt bad...Well, she broke up with me more than I broke up with her, I think."

Elon and the singer dated on and off for about four years, starting in 2018. The two share two children. In September 2021, Elon told Page Six that he and Grimes "are, I'd say, probably semi-separated," adding, "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."

In a March 2022 interview with Vanity Fair, the singer said she and Elon "live in separate houses" and are "best friends."

She later tweeted, "Me and E have broken up *again* since the writing of this article haha, but he's my best friend and the love of my life, and my life and art are forever dedicated to The Mission now." 

In 2020, Elon and then-girlfriend Grimes welcomed their first child together, a son. They soon modified the spelling of his name in order to meet California's legal guidelines, which only permit letters from the English alphabet. Switching over to roman numerals, the parents agreed to spell his name, X Æ A-Xii.

"X, the unknown variable," Grimes explained on Twitter. "Æ, my elven spelling of Ai (love &/or Artificial intelligence) A-12 = precursor to SR-17 (our favorite aircraft). No weapons, no defenses, just speed. Great in battle, but non-violent." 

Grimes continued, "A=Archangel, my favorite song" with an accompanying a rat and sword emoji. "Metal rat."

In her Vanity Fair interview, Grimes she and Elon privately welcomed a baby girl, their first daughter, 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 "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."

In 2022, Business Insider published court documents that stated Elon welcomed twins with Neuralink executive Shivon Zilis in November 2021. The babies were reportedly born in Austin, Texas, where the businessman lives. He also seemingly weighed in on the report on Twitter, writing, "Doing my best to help the underpopulation crisis. A collapsing birth rate is the biggest danger civilization faces by far."

"Mark my words," he  added, "they are sadly true."

In September 2023, a Time magazine cover story, adapted from biographer Walter Issacson's book about Elon, revealed that the pair's twins are named Strider and Azure.

The New York Times' Sept. 9 review of Walter Isaacson's biography Elon Musk states that Elon and Grimes share three children, not two as previously believed. The on-again, off-again couple at one point welcomed a child named Techno Mechanicus, nicknamed Tau, the report said.