Tech billionaire Elon Musk secretly had a third child with Shivon Zilis, project director at brain chip company Neuralink.

Musk and Zilis had twins in December 2021 through in vitro fertilization. On June 21, Bloomberg reported that the American billionaire secretly had another child with Zilis earlier this year.

On June 23, Musk confirmed the news to Page Six, but said it was not a secret because all his friends and family knew.

It is unclear how many children Musk has actually given birth to. According to information published in the media, he has 12 children, including 6 with his first wife Justine Wilson (whose first son died at 10 weeks old), 3 with artist Grimes, and 3 with Shivon Zilis.

Musk is one of the founders and CEO of Neuralink, a company specializing in developing brain-computer technology. Zilis, meanwhile, is considered a star in the American billionaire’s empire. Born in Canada, she started her career at IBM, then joined the investment fund Bloomberg Beta. She was named to Forbes’ 30 Under 30 list in the venture capital category in 2015.

Shivon Zilis met Musk at OpenAI, which he co-founded in 2015, as the youngest member of its board of directors. In 2017, she moved to Tesla as a project manager, deploying AI for self-driving cars and chip design. Zilis later became the executive director of special projects at Neuralink.

The news of their third child came a week after the WSJ published a story about Musk’s “borderline relationships” with subordinates. In it, a former SpaceX employee accused Musk of repeatedly asking her to bear his child. She refused and was subsequently denied a raise, eventually leaving the company with a severance package worth more than $1 million.

Elon Musk has frequently spoken out about the threat of declining birth rates, calling them the biggest threat to human civilization. He has said he encourages his friends to have more children. When news of Zilis’ twins broke, he explained on X that he was “doing his best to help combat the population crisis.”