Grimes was less than happy to be out of the loop following the birth of Elon Musk‘s twins with Neuralink executive Shivon Zilis.

Grimes, whose real name is Claire Boucher, was “outraged” to learn about the children — Strider and Azure — at the same time as the public, according to an excerpt of Walter Isaacson’s upcoming biography of the billionaire, as reported by the Wall Street Journal. Musk’s twins with Zilis were born weeks before Musk and Grimes welcomed their second child via surrogate in December of 2021.

The news of Musk’s twins was first reported by Insider in July of 2022.

Grimes responded to Isaacson’s reporting in an X post on Sunday, writing that she had recently spoken to Zilis about the situation and described the conversation as “long overdue.”

“I truly apologize for responding to Walter like that,” Grimes wrote. “As u can imagine, that was a very gut level reaction to a thing that has been very hard for me. Communication about the twins wasn’t handled super well in the past, but I now totally understand what happened and totally forgive the situation.”

Isaacson’s “Elon Musk,” which intimately follows the past few years of the CEO’s life, also revealed that Grimes and Musk had a third child, also via surrogate, in secret. Although the age of the child was not revealed, their name was revealed as Techno Mechanicus, or Tau for short.

Grimes also addressed Techno in her Sunday post, writing, “I wish I could show u how cute little Techno is, but my priority rn is keeping my babies out of the public eye, Plz respect that at this time.”

Musk and Grimes also share a son, X Æ A-Xii Musk, or X, and a daughter, Exa Dark Sideræl Musk, who goes by Y. In total, Musk now has 11 known biological kids with three different women.

The book, set to be released on Tuesday, also revealed behind-the-scenes decisions in regard to his Starlink satellite network during the war in Ukraine as well as Musk’s thoughts on the generative AI boom.

Representatives for Musk and Grimes did not immediately respond to Insider’s request for comment.