Billionaire Elon Musk and his Canadian singer girlfriend Grimes have apparently renamed their child.

Musk, 48, founder of aerospace manufacturer SpaceX, welcomed his child, a son, with Grimes, 32, earlier this month.

The couple attracted much public attention when they announced that they would be naming their son X A-12 .

But it seems like the couple have decided to change the unusual name of their baby after all.

In an Instagram post uploaded on Monday, Grimes, whose real name is Claire Elise Boucher, responded to a netizen who left a comment asking if the couple will change their son's name due to Californian regulations.

The state of California, where Mr Musk lives, accepts only names with the 26 letters of the English alphabet and appropriate punctuation such as hyphens, apostrophes, periods and commas. Numbers are not allowed.

Grimes said that her baby's name will be changed to X A-Xii, and added that she felt Roman numerals looked better than numbers.

It is unclear if the couple, who began dating in 2018 after meeting on Twitter, have registered their baby's name officially.

Their son is Grimes' first child while Mr Musk, who has two previous marriages, has another six sons, including the eldest son who died as an infant, with his first wife.