Though Musk, 48, confirmed the child is a boy, Grimes, 32, previously stated during a YouTube live stream in February that she doesn't want to “gender them,” allowing them to choose their own identity.
Grimes also hinted at the "genius" name they gave the baby in the same live session.
"I have a name for the baby, but I don’t want to say what it is because everyone I’ve told it hates it, and everyone’s gonna make fun of it,” she said. “But it is, in fact, a genius name, and people just don’t appreciate it yet because it’s too avant-garde.”
Musk, who's been highly active on Twitter recently, reassured followers that the mother and baby are "all good" before sharing a photo of the child with a face tattoo filter that reads "savage."
This news follows a recent report from Deadline that Musk is working with Tom Cruise and NASA to develop the first narrative feature action-adventure film shot in outer space. The project is still in the early stages, but wow, that would be unbelievable to watch.
X Æ A-12 Musk is Grimes' first child and Musk's sixth. The multi-billionaire has five other sons – a set of twins and a set of triplets – with his ex-wife, author Justine Wilson.
Likely pronounced "X Ash Archangel Musk," the odd name incorporates a ligature, Æ, standing for "ash," while A-12 is believed to be in reference to the CIA aircraft Lockheed A-12, which was internally codenamed "Archangel." There's some confusion around what the "X" means – if it means anything at all.
Unsurprisingly, a flurry of memes was sparked on social media. Here are 10 of the most creative interpretations.