San Francisco, California - Elon Musk's litter of little ones has grown once again after he and his ex-girlfriend Grimes revealed they welcomed a secret third child together.

Musk confirmed the news of his 11th child in a social media post on Saturday, sharing the tyke's name for the first time: Techno Mechanicus, or Tau for short.

The reveal comes as writer Walter Isaacson prepares to publish a biography of Musk, which will shed new light on aspects of his life, such as his past relationships.

Grimes and Musk began dating in 2018 and welcomed their son X AE A-Xii, or X for short, in May 2020. The two split in September 2021 but remained close friends.

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In March 2022, Grimes accidentally revealed their secret second child - a daughter named Exa Dark Sideræl, or Y for short.

Neither of the stars has shared any more details on the third child, such as age and sex.

According to the Los Angeles Times, the book explains that Tau is "the Greek letter representing the irrational number that is equal to two times pi," which has a numerical value of 6.28, an ode to Musk's June 28 birthdate.

Last week, Grimes posted — then quickly deleted — a message on social media aimed at Isaacson, where she pleaded with him to "tell Elon to let me see my son." She also mentioned Shivon Zilis, an executive with Neuralink that Musk fathered twins with while they were dating.

Grimes issued a lengthy response to Musk's post revealing their child's name, where she insisted that she and Zilis now "respect each other a lot."

"I wish I could show u how cute little Techno is [alien emoji] but my priority rn is keeping my babies out of the public eye," she added.

Isaacson's biography, simply titled Elon Musk, will be released this Tuesday.