In response to the report, published on Tuesday, April 15, Musk tweeted, “TMZ >> WSJ.”

A rep for Musk did not respond to PEOPLE’s request for comment.

Elon Musk with son X Æ A-12.Jeff Bottari/Zuffa LLC

For years, Musk has spoken publicly about his fears that society will undergo an “underpopulation crisis.”

“I can’t emphasize this enough, there are not enough people,” he said during a 2021 event with the Wall Street Journal. “And I think one of the biggest risks to civilization is the low birth rate…If people don’t have more children, civilization is going to crumble.”

After welcoming twins with Neuralink executive Shivon Zilis, he seemingly alluded to the news on social media by writing, “doing my best to help the underpopulation crisis.”

When previously asked by Mark Cuban about how many children he planned on having, Musk — who is still actively focused on making it to Mars with SpaceX — reportedly replied that “Mars needs people.”

Elon Musk and Shivon Zilis with their twins Strider and Azure.Shivon Zilis/X

In February 2025, St. Clair posted an announcement to X saying that she and Musk welcomed a child together in September 2024.

According to the WSJ’s report, the results of Musk’s paternity test in their custody case, determined his “Probability of Paternity” was 99.9999%. A spokesperson for St. Clair confirmed to PEOPLE that a paternity test showed there is an almost 100% probability of paternity.

Musk first became a father in 2002 when ex-wife Justine Wilson welcomed their son Nevada Alexander, who died at 10 weeks old. The two went on to have five more children: twins Vivian and Griffin, 20, and triplets Kai, Saxon and Damian, 19.

Elon Musk carries his son X Æ A-Xii on his shoulders in the Oval Office of the White House in Washington, DC, on February 11, 2025.JIM WATSON/AFP via Getty

He shares three children with his ex Grimes, sons X Æ A-12 and Techno Mechanicus as well as daughter Exa Dark Sideræl. Additionally, he has three children with Zillis: twins Strider and Azure and daughter Arcadia.