Elon Musk’s eldest child with ex Grimes, X Æ A-Xii, is all smiles in a new pic his dad shared on his fourth birthday.

The billionaire Tesla CEO posted the photo of the boy, nicknamed X, on the social media platform he owns, X, formerly Twitter. Musk captioned the post, which shows the child sitting on what appeared to be a reception desk, “Lil X turns 4 today on May 4th.”

The Space X founder, a father of 11 and one of the top three richest people in the world, rarely shares pics of his kids on social media. He has occasionally been photographed out with X, most recently in March during a visit to Tesla’s electric car plant in Gruenheide, Germany.

In addition to X, Musk and Grimes, who broke up in 2022, are also parents to Exa Dark Sideræl, or Y, 2, and Techno Mechanicus, or Tau, whose birth was confirmed in 2023.

Musk, 52, also fathered six children with ex-wife Justine Wilson Musk: Twins Vivian and Griffin, 19, triplets Kai, Damian, and Sax, 18, and eldest child, son Nevada, who tragically passed away at age 10 weeks in 2002.

In 2021, the businessman welcomed twins Strider and Azure. with Neuralink executive Shivon Zilis. She has occasionally shared pics of their kids on her own X account.

In April, Musk jokingly reflected on his parenting journey on X. “Whoa,” he wrote, “I just realized that raising a kid is basically 18 years of prompt engineering.”

Elon Musk is a Stanford dropout, CEO of Spacex and Tesla, and one of the richest men in the world.