Elon Musk and one of his top executives secretly had twins in November, according to a report Wednesday by Insider. The revelation came in court documents petitioning to have the children's last name changed to Musk.
The petition, signed by Musk, the CEO of Tesla and SpaceX, and Shivon Zilis, director of operations and special projects at Musk's private neurotech startup, Neuralink, was approved by a judge in Austin, Texas, in May. The 36-year-old Zilis previously worked as project director in the CEO's office at Tesla.
The nature of their relationship wasn't immediately clear. Zilis formerly lived in San Francisco, but she bought a house in Austin about three months before the twins were born, Insider reported. The heavily redacted name-change petition lists that address for both Musk and Zilis, Insider reported.
Musk didn't respond to a request for comment. Zilis couldn't be reached for comment.
In a series of tweets Thursday, Musk didn't directly address the Insider report or publicly acknowledge the twins as his children. He instead made indirect quips such as "Doing my best to help the underpopulation crisis" and "I hope you have big families."
News that Musk, 51, had children with one of his direct reports comes less than two months after Insider reported that SpaceX had paid a flight attendant $250,000 to settle allegations that the billionaire exposed himself to her during a flight. Musk later denied the allegations, calling them "utterly untrue."
Musk, an outspoken advocate for population growth, now has nine children. Musk previously tweeted about declining birth rates in 2017, saying: "The world's population is accelerating towards collapse, but few seem to notice or care."
In May, Musk tweeted a Wall Street Journal graphic tracking a "fertility slump" in the US since 1940.