The longtime girlfriend of a Texas oil tycoon is suing him in New York federal court, claiming he reneged on promises of financial support after he left her to marry another woman.
The former girlfriend, Oona O. Sperr, an interior designer, said she gave up her career during her relationship with Sid Bass, 84, a thrice-married billionaire whose first two wives were patrons of the New York City arts scene, according to the complaint.
His first marriage, to Anne Hendricks Bass, ended in 1988, with Ms. Bass receiving at least $200 million and more than a million of his shares in Disney — reportedly the largest divorce settlement in Texas history at the time.
Ms. Sperr, 64, said she was Mr. Bass’s companion from 2014 to 2024, managing multiple Upper East Side townhouses he owned, wearing a 25-carat diamond he had given her on her ring finger and being introduced at society parties as either his wife or partner.
But the pair never formally married, and, according to the complaint, shortly after Mr. Bass was diagnosed with Parkinson’s, he asked her for a separation and then married Althea Irene Viafora Kress, 68.
Ms. Sperr is also suing Ms. Viafora Kress in the same suit, accusing her of manipulating Mr. Bass, taking advantage of his cognitive decline and actively directing him to cut Ms. Sperr off financially. Mr. Bass is worth at least $4.4 billion, according to the complaint.
While Mr. Bass’s first two wives received generous settlements and homes when the relationships ended, Ms. Sperr has significantly less leverage since she can’t go to divorce court. In her suit, she argues that her devotion, trust and the fact that she abandoned her career to make Mr. Bass the center of her life for a decade should entitle her to a comparable payout. She is asking for $400 million.
The lawsuit punctuates a series of high-profile separations for Mr. Bass. When he left Ms. Bass for the socialite Mercedes Kellogg four decades ago, he found himself at the center of one of the defining high-society furors of 1980s New York. Their split came after he and Ms. Kellogg were discovered together at the Hôtel Plaza Athénée in Paris.
Mr. Bass later married Ms. Kellogg, a prominent donor to the Metropolitan Opera who also served as its longtime managing director. Their wedding was held in 1988 at the Plaza Hotel in New York, just a few months after his younger brother, Robert Bass, sold the property to Donald Trump for $390 million.
In 2011, after 23 years, they also split, and in January 2014, according to the complaint, Mr. Bass invited Ms. Sperr to lunch at his townhouse on East 94th Street and suggested she never leave.
“At that lunch in Manhattan, and in conversations in New York in the days and weeks that followed, Sid made clear, and Oona agreed, that they would build their lives together,” the complaint reads. She gave up her career, it says, confident that Mr. Bass would provide for her.
“This is a case about broken promises,” said Roberta Kaplan, Ms. Sperr’s lawyer. “Sid Bass is a billionaire at least four times over. Oona is the woman who spent a decade making Sid’s life convenient.” She added that Ms. Sperr “had no choice but to bring this case.”
Mr. Bass and Ms. Viafora Kress did not immediately respond to requests for comment on the lawsuit.
Ms. Sperr says in the complaint that she did not realize Mr. Bass had begun seeing Ms. Viafora Kress and was stunned when he informed her, in September 2024, that he wanted a separation and said she should move out. He verbally offered her a lump-sum payment of $50 million to do so, and promised to give her both a home in New York and an additional property of her choosing, the complaint reads. Mr. Bass also said he would continue to provide care for her mother, according to the lawsuit.
Ms. Sperr argues that less than a month later, however, she received a letter from Mr. Bass’s lawyers titled “Maintenance Agreement,” which instead of the $50 million lump sum offered her a series of $5 million annual payments over a 10 years, “thereby materially reducing both the reliability of such payments and their net present value,” she argued in the complaint, adding that she would be “forced to depend entirely on Sid’s increasingly unpredictable whims.”
The letter also “denied Oona ownership of any home, conditioned her housing on tenancy, rather than title, abandoned his commitment to pay for her mother’s care” and also required that she sign a nondisclosure agreement.
At the time, Mr. Bass was already in a relationship with Ms. Viafora Kress, according to the complaint. They married in August 2025, which Ms. Sperr was notified of in an six-sentence email with the subject line “news.”
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