Grimes and Elon welcomed their second child via surrogacy in 2021, Grimes revealed in a Vanity Fair interview. Later on, she shared that she hadn't planned on revealing the existence of her second child in the story. "Def held back a lot, contrary 2 headline," she tweeted a few days after the piece was published, per CNN. "& 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."
The baby was originally named Exa Dark Sideræl Musk, though now her nickname — Y — appears to be her new official moniker.