Singer Grimes has revealed she has welcomed a secret second child with on-and-off Tesla billionaire partner Elon Musk – with an equally unconventional name to match their firstborn.

Grimes, real name Claire Boucher, was forced into the revelation in an interview with Vanity Fair when the journalist heard a baby crying from upstairs.

The pair welcomed baby girl Exa Dark Sideræl, who Grimes and Musk have nicknamed ‘Y’, via surrogate in December 2021.

Grimes explained she decided to turn to surrogacy because of difficulties in her pregnancy with their son X Æ A-12 in 2020.

“He was pressing on my nerves, so I kept collapsing,” she said of the last month of the pregnancy.

“I took a few steps and collapsed. It was kind of scary.”

Tweet from @VanityFair

The shock announcement comes just months after Grimes and Musk announced their separation.

At the time of the interview, it seemed that Grimes and Musk had reunited in some capacity.

“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,” she said.

“We just have our own thing going on, and I don’t expect other people to understand it … this is the best it’s ever been.”

While her fans celebrated the addition to their family, Grimes took to Twitter hours after the article’s release to again clarify her and Musk’s ever-complicated relationship status.

“Me and E have broken up *again* since the writing of this article haha, but he’s my best friend and the love of my life, and my life and art are forever dedicated to The Mission now,” she said in a now-deleted tweet.