Shivon Zilis tells jury that Elon Musk was her twins' secret IVF donor — until Business Insider found out

• It's week two of Musk v Altman, in which the Tesla CEO seeks $134B from OpenAI and Microsoft.
• Former OpenAI board member Shivon Zilis took the stand as a key witness for Musk.
• First order of business: clearing the air on their complicated and once-secret relationship.

Former OpenAI board member Shivon Zilis was asked under oath on Wednesday to clear the air about her complex, once-secret relationship with Elon Musk.

Zillis, a decadelong executive at Musk's companies and the mother of four of his children, testified as a witness in the ongoing Musk v Altman trial in federal court in Oakland.

She said sometime after she joined OpenAI in 2016, she had a romantic "one-off" with Musk, a cofounder and major investor in the company.

They then became friends, she said — and co-parents.

Zilis, an OpenAI executive until 2023, said she kept the paternity of her twin son and daughter hidden from OpenAI's board — until Business Insider revealed his role in a story the following year.

"We initially agreed on complete confidentiality of the donation," Zilis told the jury in Musk's civil trial against AI rival Sam Altman.

"And I got a call from an unknown number one morning, and it was Business Insider," Zilis said.

"They had somehow gotten sealed court documents illegally that shared the genetic fraternity of my children, and they said they're going to publish them later that day."

Business Insider's story was based on publicly available court documents showing that Zilis and Musk had filed a petition to change the twins' names in order to "have their father's last name and contain their mother's last name as part of their middle name." The order was filed in a district court in Travis County, Texas, and approved by an Austin judge.

Name-change petitions are public documents in Texas, subject to redactions for home addresses, driver's license numbers, and social security numbers. The petition obtained by Business Insider had such redactions and was signed by Musk and Zilis.

Zilis is a key witness in the trial, in which Musk has alleged "unjust enrichment" over OpenAI's for-profit transition. Musk asserts that OpenAI took his $38 million early donations on the false promise that the company would remain a nonprofit dedicated to the public good. Altman, as its CEO, and Greg Brockman, as its president, are also potentially on the hook for any cash damages.

On the witness stand Wednesday morning, Zilis said she decided to have kids with Musk in late 2020 or early 2021 after he offered to donate his sperm.

Musk had been "encouraging everyone around him to have kids," she said, adding that he said, "that if I was ever interested, he'd be happy to make a donation."

Zilis said she and Musk have since been "romantically involved," and described a life of suburban bliss when the father of her now-four children is in town and not working.

"We do live together when traveling, and we've been spending family time in Austin," said Zilis of Musk, adding that he is "in part" supporting the children.

"I'm sure it's not surprising to anyone," she told jurors of her and Musk's decision to keep the twins' parentage secret.

"There's just an insane kind of, just security risk that he bears with him," she said.

"And if he was indeed just a donor, it didn't seem fair to the kids to have them bear that burden their whole lives, if there wasn't the upside of fatherhood with it."

After the call from Business Insider, her first phone call was to her father and her second call was to Altman, Zilis testified. Board members quickly agreed to keep her on the board, she added.

The awkward testimony, under questioning by an attorney for Musk — Zilis appeared uncomfortable, even emotional at times — set the scene for a detailed account of her interactions with Musk and the OpenAI board, which she joined in 2020.

She denied that she filled Musk in on OpenAI's private licensing negotiations with Microsoft in 2021 through 2023.

She was asked if her "personal connection" with Musk ever impacted her role as a board member. "It did not," she said.

She was also shown a text exchange with Musk from 2018, around the time he left the OpenAI board, but before he left OpenAI.

"Do you prefer I stay close and friendly to OpenAI to keep info flowing or begin to disassociate? Trust game is about to get tricky so any guidance on how to do right by you is appreciated," Zilis asked Musk in a text shown to jurors.

"Close and friendly," Musk responded. "But we are going to actively try to move three or four people from OpenAI to Tesla. More than that will join over time, but we won't actively recruit them," Musk responded.

"That's just a thing I wanted to figure out how to navigate," Zilis told the jury of the text exchange. "If I was still going to be in a position of being a facilitator or a bridge."

Altman, she said, knew and approved of her keeping Musk in the loop at the time. But after she herself joined the board in 2020, she did not act as a "funnel" of information to Musk, she testified.