What just happened? Newly discovered court documents have revealed that Elon Musk had twins with a top executive at his AI startup Neuralink last year, bringing the number of known children fathered by the world's richest man to nine.

The documents, seen by Insider, show that Musk, 51, and Shivon Zilis, 36, filed a petition in April to change the twins' names in order to "have their father's last name and contain their mother's last name as part of their middle name."

Zilis reportedly gave birth in Austin, Texas, in November 2021, weeks before Musk and singer Claire Boucher, better known as Grimes, had their second child via a surrogate. It means Musk has nine children with three different women—he shares five with ex-wife Justine Wil.

The CEO has long been a proponent of increasing the global birth rate, warning that it has been below minimum sustainable levels in the US for around 50 years, which could cause civilization to crumble. "I mean, I'm doing my part haha," he recently tweeted.

Markham, Ontario-born Zilis' LinkedIn page lists her as director of operations and special projects at Neuralink, having previously worked at IBM and venture-capital fund Bloomberg Beta. She is also a board member at artificial-research firm OpenAI, which Musk co-founded, and was on Forbes' 30 Under 30 list in the venture-capital category in 2015. Zilis has also been floated as one of the people Musk could appoint to run Twitter after his acquisition, assuming it ever completes.

Earlier this year, one of Musk's children petitioned to change their name and receive a new birth certificate, stating that "I no longer live with or wish to be related to my biological father in any way, shape or form."

Neither Musk nor Zilis has commented on the story.