ST. LOUIS — Tech billionaire and Clayton native Sam Altman is accusing his estranged sister of defamation over her claims that he repeatedly sexually assaulted her when they were children.

Altman, the CEO of OpenAI, said in a countersuit filed Friday that his sister, Ann Altman, has spent years making repeated false sexual assault claims in order to pressure her family into giving her more money than they've already provided.

"This action was filed to try to embarrass Sam Altman in the eyes of the public and in his community," the countersuit says.

But Ann Altman's attorney, Ryan Mahoney, said her lawsuit tells the real story.

"Sam Altman's counterclaims are as predictable as they are unfortunate," he said in a statement. "We see this all too often in cases of this nature as a way to distract from the true issues in the case and as a means of bullying the plaintiff."

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Sam and Ann Altman grew up in Clayton, the children of an attorney and a dermatologist. A 2007 story in the Post-Dispatch called Sam Altman a rising star in the tech world and noted he became fascinated with computers at a young age.

He did not address his relationship with his sister publicly, but for years, she claimed in social media posts and in a book of published poems that Sam Altman sexually abused her.

In January, she filed a lawsuit claiming he groomed, manipulated and assaulted her in the 1990s and 2000s. The incidents caused post-traumatic stress disorder and physical injury, the suit says.

The Post-Dispatch does not typically identify people making claims of sexual assault, but Ann Altman agreed to be named.

On Friday, Sam Altman's lawyers filed a countersuit calling his sister's claims "entirely fabricated" and designed to get even more money than the regular payments distributed to her from their father's trust.

Sam Altman is seeking $1 in damages for his suit. He "does not want to harm his sister financially but does want a verdict in his favor that the statements by Plaintiff are not true," the filing says.

A hearing has not yet been set in the case. Ann Altman's lawyers will file a response to Sam Altman's claims in the coming weeks.

Post-Dispatch photographers capture hundreds of images each week; here's a glimpse at the week of March 2, 2025. Video edited by Jenna Jones.

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