Elon Musk has posted on Twitter as rarely a photo of his 2-year-old son X Æ A-12, who came to life from the owner's relationship with singer Grimes. In one photo, the baby is seen smiling in front of a heart-shaped sculpture in San Francisco.

Elon wrote the photo side, "X in beautiful San Francisco."

So much so, in another post, Elon shared a photo of x's entry card in his new office, writing, "And with his Twitter badge.""

Along with X, Elon has daughter Exa "Y" Dark Sideræl, 12 months old, with Grimes. He and the singer welcomed their youngest child through a surrogate mother in December.

In addition to X and Y, Elon is a father to twins Vivian and Griffin, 18, and trainees Kai, Damian and Sax, 16, with his first wife Justine Wilson.