No one is more shocked by yet another baby announcement from Elon Musk than his oldest daughter Vivian. Apparently, the 21-year-old learned along with the rest of the world that she has a new half-sibling when the news broke on social media that the Space X CEO welcomed his fourth child (and 14th overall) with

Elon Musk has welcomed his fourteenth child, and his fourth baby with Shivon Zilis. The pair welcomed their second son together, Seldon Lycurgus.

“Discussed with Elon and, in light of beautiful Arcadia’s birthday, we felt it was better to also just share directly about our wonderful and incredible son Seldon Lycurgus. Built like a juggernaut, with a solid heart of gold. Love him so much," Zilis wrote, also revealing the name of the couple's previously-born child in the announcement.