Elon Musk Secretly Welcomed a Second Child Musk's partner, musician Grimes, shared in an interview that the couple welcomed a daughter last December.

Elon Musk has never been one to keep things secretive, especially when it comes to tweeting out his sometimes contentious opinions and updates about Tesla products and plans.

But when it comes to his personal life, it looks like he might be a little more private.

His ex-partner, musician Grimes, revealed in an exclusive interview with Vanity Fair that the pair welcomed their second child via surrogate last December.

This is the first daughter for the couple, named Exa Dark Sideræl Musk.

Related: Elon Musk and Grimes Officially Split 'On Great Terms'

"Didn't mean for them 2 find out about my daughter so please respect her privacy as I'd love her to be able to live as private of a life as possible," Grimes tweeted out after the release of the interview, telling fans that she didn't intend for the story to be centered around her private life but rather her new music.

Musk and Grimes also share a son together named X Æ A-Xii (or "X" as he is nicknamed) who was born in May 2020.

In the interview, Grimes (whose real name is Claire Boucher) opened up about her difficult pregnancy with X.

"[X] was pressing on my nerves, so I kept collapsing. I took a few steps and collapsed," she told Vanity Fair. "It was kind of scary, because you don't want to fall a lot when you're eight months pregnant. So I would just crawl to the bathroom and crawl back or whatever."

She also told the outlet that her and Musk have "always wanted at least three or four" children and plan to have more in the future,

As for the current status of their relationship? Complicated yet in a peaceful manner, if that makes sense.

Related: Grimes Shares Rare Video of Her and Elon Musk's Son

"There's no real word for it. I would probably refer to him as my boyfriend, but we're very fluid. We live in separate houses. We're best friends. We see each other all the time…. We just have our own thing going on, and I don't expect other people to understand it.," she told the outlet.

The pair made their official split public last September when Musk spoke to Page Six.

"We are semi-separated but still love each other, see each other frequently and are on great terms," Musk told the news outlet in a statement. "It's mostly that my work at SpaceX and Tesla requires me to be primarily in Texas or traveling overseas and her work is primarily in LA. She's staying with me now and Baby X is in the adjacent room."

Musk and Grimes were officially together for three years, making their first public debut at the Met Gala in 2018.

Musk also has five other children from a pervious marriage — twins Xavier and Griffen and a pair of triplets named Damian, Kai and Saxon.

Grimes' opinion and love for Musk however goes beyond just their personal relationship — she continued to praise his work ethic and contributions to society.

"Bro might say a lot of stupid shit, but he does the right thing," she told Vanity Fair.

As of early Friday afternoon, Musk's net worth was an estimated $221.2 billion.