Shivon Zilis testified Wednesday in a federal courtroom in Oakland, California, that Elon Musk offered to donate sperm to her in 2020 and that she accepted because she still really wanted to be a mum. Her testimony came in Musk's lawsuit seeking to reverse OpenAI's move to a for-profit company.

Zilis said she and Musk had a one-off romance about a decade ago, but that they were not romantically involved in 2020 when he made the offer. She also said they agreed to keep his paternity strictly confidential for the first two children she had by him.

The testimony put one of Musk's closest former collaborators at the center of a trial that reaches into the politics of OpenAI itself. Zilis joined the company as an adviser in 2016, became a director from 2020 to 2023 and left the board in March 2023, the same month Musk launched xAI.

That timeline matters because OpenAI lawyers have suggested Zilis funnelled information about the company to Musk after he left in 2018. Zilis has denied giving him paternity information early, saying she did not tell OpenAI chief executive Sam Altman that Musk was the father of her twins until 2022, after learning a Business Insider report was imminent, because of the confidentiality agreement.

Altman and OpenAI president Greg Brockman wanted to keep Zilis on the board, Brockman said, adding: “We trusted her to keep the Elon conflict under control.”

Zilis's testimony also showed how closely Musk remained tied to her life after years of secrecy. She said Musk is now an active participant in the lives of their four children and that they spend a few hours a week together as a family.

Behind the courtroom drama is a broader fight over OpenAI's future and Musk's effort to force it back from a for-profit structure. Zilis, who has worked as a venture capitalist in Silicon Valley for more than 15 years and held executive positions at Tesla and Neuralink, became a crucial witness because her ties to Musk and OpenAI crossed the same high-stakes circle the case is now probing.

The unanswered question is not whether Zilis knew both sides well. It is how much her overlapping roles helped Musk understand OpenAI from the inside before the company split into a legal and commercial adversary.