Elon Musk and Grimes forced to reveal the latest addition to their family

Despite splitting last year, Elon Musk and Grimes have welcomed a new baby girl. Photo / Getty Images

Elon Musk and Grimes have welcomed another child.

The couple split last year after three years together but have reunited in some capacity after welcoming their daughter into the world via surrogate.

Grimes revealed during her Vanity Fair cover story published this week that the baby who could be heard crying in the background during her interview, was not their son, X, but the latest addition to their family.

"I don't know. I don't know what I was thinking," she told Vanity Fair after being caught trying to hide her daughter's existence.

The singer later revealed their daughter, who was born in December last year is called Exa Dark Sideræl but they call her Y for short.

When asked how the on-again couple were managing their relationship in light of a new child, Grimes said, "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.

"This is the best it's ever been," she explained, "We just need to be free."

Speaking to Page Six last year, 50-year-old Musk commented on their split saying, "We are semi-separated but still love each other, see each other frequently and are on great terms."

During Grimes' Vanity Fair interview, she hinted there may be more children in the future for the pair, explaining they have "always wanted at least three of four" children together.

While the couple share a son and daughter together, Musk is father to five sons - Griffin and Xavier, 17-year-old twins and Damian, Saxon and Kai, 16-year-old triplets, whom he shares with his ex wife, Justine Wilson.

Musk has also been married to Westworld actress Talulah Riley, first in 2010 before divorcing in 2012 and reconciling and remarrying in 2013, then divorcing again in 2016.