Elon Musk's son makes high-profile visit to the Oval Office. His mom, Grimes, isn't pleased The Oval Office generally maintains a rather formal air. But when Elon Musk's 4-year-old son, X Æ A-Xii (known as X), waltzed in on Feb. 11, he made himself right at home.

Grimes, Musk’s former partner and mother to three of his 12 children, was seemingly less than thrilled when she found out via social media about her son’s public appearance.