Business Insider reported that Elon Musk, CEO of Tesla and SpaceX, and the world’s wealthiest man, welcomed twins with a Neuralink executive last year.

Musk posted a tweet on May 24, saying that “USA birthrate has been below minsustainable levels for 50 Years” and pinned it at the top of his more 100 million-follower account. He quietly fathered the children alongside Shivon Zilis who works for Musk at the company, which hopes to create an implantable computer chip to help the human brain. According to documents obtained to Business Insider

The outlet was able to obtain court filings regarding the modification of the children’s legal name to include the Musk last and Zilis as the middle names. CNN Business was unable to confirm the content of the documents. However, a Travis County court docket, Texas obtained by CNN Business showed that the name change petition had been filed in April 2022, and granted in May. This matches the dates published by Business Insider. These documents include Musk’s signature and the stamp of the court, listing him as the father as well as Zilis as his mother.

Musk didn’t immediately respond to the requests for comment made to SpaceX, Tesla and Neuralink representatives.

According to Zilis’ LinkedIn profile, her professional connections to Musk date back at least to April 2016, when she was an advisor to OpenAI. Musk is one cofounder of OpenAI, an open-source research laboratory that aims to benefit all people.

Musk hosted a livestreamed event in August 2020 to show the progress of Neuralink’s technology. It had placed its technology in a pig. Nearly one year later, Neuralink claimed that monkeys could play Pong once the chips were implanted into their brains. However, Neuralink had to address concerns regarding its testing practices. It denied allegations of animal cruelty and confirmed earlier this year that monkeys had died during the testing.

LinkedIn says that Zilis worked at Tesla and Neuralink starting in May 2017. She currently serves as director of operations and special project for Neuralink. OpenAI’s board was made up of Zilis in 2020. Before joining Musk-helmed businesses, Zilis was a board member at OpenAI. At least two other organizations that deal with artificial intelligence have had Zilis on their boards. Zilis didn’t immediately respond to our request for comment.

This is the second set that Musk is believed to have fathered. Justine, Musk’s first wife, had twins in 2004, and then welcomed triplets two-years later. The couple, who had been married from 2000 to 2008. They lost their first child. Justine, an author, wrote famously about the difficulties of being married to Musk and how it felt to divorce him for Marie Claire magazine. Musk had two more children with Claire Boucher, better known as Grimes. Through a surrogate, their second child was born December 2021.