A report about Musk's relationship with the exec emerged this week, revealing he welcomed the twins in November 2021 with Shivon Zilis, of Musk's company Neuralink.
The babies' arrival came just one month before Musk had a baby via surrogate with Grimes, who he split up with in September 2021.
Court records cited by Insider showed Musk and Zilis had filed to change the twins' last names to Musk's and kept their mother's name as part of their middle names, and that a Texas judge approved the petition the following month.
With the report apparently having broken the news to the world, Musk responded in exactly the way you might expect: with a tweet.
In response to the news, the SpaceX CEO managed to both apparently confirm the happy news of welcoming two new children while also plunging humanity into a pit of dread.
He wrote: "Doing my best to help the underpopulation crisis. A collapsing birth rate is the biggest danger civilization faces by far."
Musk added a follow-up which further warned Twitter users about the end of civilisation, potentially encouraging others to start thinking about joining him in popping out some children.
He wrote: "Mark my words, they are sadly true."
The arrival of the twins brings Musk's total count of children to nine, including two children he shares with Grimes and five he shares with his ex-wife Justine Wilson.
Zilis is identified on LinkedIn as being director of operations and special projects at Neuralink, which Musk co-founded in July 2016. Zilis began working at the company the following year, while also being named a project director in artificial intelligence at another of Musk's companies, Tesla.
A threat to civilisation is an explanation Musk has previously offered when questioned about his children, having said at a Wall Street Journal virtual event in December 2021 that 'there are not enough people'.
"There are not enough people, I can’t emphasise this enough. There are not enough people... If people don’t have more children, civilization is going to crumble. Mark my words."
Musk then joked that he tries to 'set a good example' with his children, adding: "Gotta practice what I preach.”Featured Image Credit: Alamy