Grimes and Elon Musk have secretly welcomed a third baby together, and his name is just as unique as his big brother and sister’s.

According to a new biography on the Tesla CEO’s life, the couple have had a third baby – a little boy, named Techno Mechanicus. The couple also share another son named X Æ A-XII, or ‘X’, who was born on May 4, 2020.

They also welcomed a daughter via surrogate in December 2021, named Exa Dark Sideræl, who is nicknamed ‘Y’. The couple went their separate ways in 2021 after three years together.

According to The New York Times’ review of the biography by journalist Walter Isaason, their third child goes by the nickname ‘Tau’.

Elon Musk and Grimes’ children

Grimes, whose real name is Claire Boucher, revealed that she and Elon secretly welcomed their daughter via surrogate in December 2021, during an interview with Vanity Fair. The couple had been keen to keep their new arrival out of the limelight, until the baby was overheard crying during the interview.

“I don’t know. I don’t know what I was thinking,” Grimes said after trying to conceal her bundle of joy.

The 35-year-old revealed her daughter’s name is Exa Dark Sideræl, but they call her Y. Her older brother’s name is pronounced X A.I. Archangel, but he’s known as X.

While Elon and Grimes separated in 2021 after three years together, it appears they did get back together. Kind of.

“I would probably refer to him as my boyfriend, but we’re very fluid,” Grimes told Vanity Fair. “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.

“This is the best it’s ever been. We just need to be free.”

At the time the singer admitted there were plans for more babies in the future, saying they’ve always wanted three or four children.

Elon has six sons with his former wife Justine Wilson: twins Griffin and Xavier, 18, and triplets Damian, Saxon and Kai, 17. The pair’s first son, Nevada Alexander, died from sudden infant death syndrome at 10 weeks old.

It’s also believed Elon secretly welcomed a set of twins, son Strider and daughter Azure, with Shivon Zilis in November 2021.