Tesla and SpaceX CEO and the world's richest man Elon Musk welcomed twins last year with an executive at another of his company, Neuralink, Business Insider.

Musk, who posted a tweet on May 24 saying that "the USA birth rate has been below the minimum sustainable level for ~50 years" and pinned it at the top of his 100-million-follower Twitter account did

Sivon Zillis, according to documents obtained by Business Insider, who works for Musk at the company that hopes to develop an implantable computer chip for the human brain.

The outlet obtained court filings related to changing the children's legal names to include the Musk last name, and Zillis as part of middle names.

CNN Business could not independently verify the contents of the documents, but a Travis County, Texas court docket obtained by CNN Business indicated

The name change petition was initially filed in April 2022 and granted in early May - matching the dates on documents published by Business Insider.

Those documents bear the court's seal as well as Musk's signature, which lists him as the father and Zillis as the mother.

Musk did not immediately respond to requests for comment sent to representatives for Tesla, SpaceX and Neuralink.

Zilis's professional relationship with Musk dates back to at least April 2016, according to her LinkedIn profile, when she became an advisor to OpenAI.

Musk is one of the co-founders of OpenAI, a non-profit research laboratory with a stated mission to "ensure that artificial general intelligence benefits all of humanity."

In August 2020, Musk held a live-stream event aimed at showcasing the progress of Neuralink's technology, which he had implanted in a pig.

About a year later, Neuralink claimed that monkeys could play Pong once the company's chips were put into their brains. But, recently, Neuralink has had to address concerns about its testing practices

Denying allegations of animal cruelty, it confirmed earlier this year that the monkeys had died as part of the trial.