Last month, we told the story of Anne Hendricks Bass, the woman who met Sid Bass at a birthday party when she was nine, spent 22 years building two cultural empires alongside him, and received a $200 million settlement when the marriage ended in 1988.
But now, a juicy new chapter in the Bass story is now being written in federal court.
On August 31, 2026, a 64-year-old New York interior designer named Oona Sperr filed a 98-page federal complaint in the Southern District of New York against Sid Bass and his new wife, seeking at least $400 million.
The complaint alleges that Sperr spent a decade as Bass’s domestic partner, gave up her career at his request, managed his homes, wore his 25-carat diamond on her ring finger, and was introduced as his wife at society events across New York, all on the strength of a promise that she and her elderly mother would be financially secure for life.
Then, one morning in September 2024, Bass told her at breakfast to pack her things.
He married yet another woman less than a year later.
Sperr says she learned about the wedding through a six-sentence email from his account with the subject line “News.”
Her complaint alleges he didn’t write it. Bass has not yet filed a substantive response, and the allegations remain untested.
Now, the complaint begins with a breakup…
But the real story begins nearly a decade earlier, when an interior designer entered Sid Bass’s world and gradually made herself indispensable to it.
The Designer
Oona Sperr’s world before Sid Bass was smaller than his but built on its own foundations.
Her father, Otto Sperr, was a Philadelphia architect. Her mother, Portia Sperr, was a Montessori educator who looked at the cultural institutions of 1970s Philadelphia and decided that none of them were designed for the people who needed them most: young children.
In 1976, Portia founded the Please Touch Museum, starting with a 2,200-square-foot exhibit space at the Academy of Natural Sciences. The founding idea, that children should learn through hands-on exploration rather than being told not to touch anything, was radical enough at the time that she had to build the institution herself because nobody else would.
Oona grew up in that household, attended the Baldwin School in Bryn Mawr, studied architecture in New York, and established an interior design practice.
She was the daughter of a builder and an institution-founder, which meant she understood both the physical and organizational labor required to make ambitious spaces function.
That background would matter enormously once she entered Sid Bass’s orbit, because managing a billionaire’s domestic life is closer to running a small company than it is to keeping house.
She and Bass had known each other since 1995.
According to the complaint, the relationship that would reshape her life began over lunch at his townhouse on East 94th Street in January 2014. At some point during the meal, he suggested she should never leave.
What followed, according to the filing, was a decade-long arrangement in which Sperr reorganized her entire professional and personal life around Bass’s. She stopped pursuing independent design work, managed their residences, supervised renovations using her professional training, coordinated staff, handled logistics across multiple properties, organized their social calendar, and traveled with him constantly.
Bass gave her a 25-carat diamond, which she wore on her ring finger.
He introduced her at events as his wife or partner. They appeared, by every available social metric, to be married.
But they were not married. New York abolished common-law marriage in 1933, and no amount of shared life creates a legal spouse under state law.
The diamond carried emotional weight and zero legal title, a distinction that would become the most expensive fact in Oona Sperr’s life.
The Promise
Sperr says it began over lunch in Manhattan in January 2014, when Bass invited her into his East 94th Street townhouse and asked, “How about you never leave?”
What followed, according to her complaint, was not simply an invitation to move in. She says the two agreed that she would build her life around his, while he would make sure she (and eventually her elderly mother) would never have to worry about money.
Sperr acted as though the arrangement were permanent.
She left her independent design career behind and began running the domestic world around Bass: supervising renovations, managing properties and staff, traveling with him and caring for him through serious health problems.
The complaint says the couple shared a bank account and planned their wills and end-of-life arrangements together. Bass made her his power of attorney and healthcare proxy, according to the filing.
For ten years, none of this apparently required a courtroom definition.
Then Bass told her to pack.
Now, before we get into the nitty-gritty of the actual case, we must remember that the Sperr filing arrives against the backdrop of Bass’s two earlier marital separations, both of which ended within the legal framework of divorce law.
As we described in the aforementioned article, Anne Hendricks Bass spent 22 years as Sid’s wife before their marriage ended in 1988. Anne received at least $200 million, Disney shares, and homes under Texas community-property law.
She built a second life as an independent patron and documentary filmmaker and died in 2020 with a collection that Christie’s sold for $363 million.
Then, Mercedes Bass spent 23 years as Sid’s second wife before they divorced in 2011. She kept substantial residential interests and her position at the Metropolitan Opera.
Both women entered their separations with the legal status of wives. Property settlements could be negotiated inside a system built to recognize marriage and divide the financial consequences of ending one.
But Sperr had spent ten years living inside many of the same arrangements… without ever becoming Mrs. Bass, unlike his first two wives.
And that difference now sits at the center of her lawsuit.
The Fine Print
Once Bass told her to leave, the previous ten years began to look different.
The renovations Sperr had supervised were no longer simply renovations. The properties she managed, the staff she coordinated, the clients she stopped taking and the career she allowed to recede all became part of a much harder question:
What, exactly, had she been doing in exchange for the security Bass allegedly promised?
New York law makes that distinction matter.
In Morone v. Morone, the state’s highest court ruled that years of living together do not automatically give an unmarried partner the financial protections of a spouse. A couple can make a binding agreement, but the person claiming one existed has to show that there really was a bargain.
Sperr says there was.
She’d arrived in Bass’s life with an established design career. Over time, she says, she stopped working independently.
Rather, she directed those skills toward his homes instead, overseeing renovations, managing properties and helping run a household that required considerable professional labor.
That gives her something more concrete than a decade of companionship. The harder question is what Bass promised in return.
Lifetime security sounds clear enough when two people expect to remain together. It becomes less clear once lawyers start asking how much money, which property, how long the support would last and what exactly was supposed to happen if the relationship ended.
For most of the decade, Sperr says they never had to answer those questions.
On the morning Bass broke up with her, they suddenly did.
And according to Sperr, Bass answered with a number: $50 million.
The Offer
Sperr says Bass told her she would receive $50 million in cash, a New York home and another property of her choosing.
He allegedly promised continued help from household staff as well, along with financial support for her 96-year-old mother.
For the first time, the lifetime security Sperr says had hovered over their relationship for years came with a dollar figure and addresses attached.
Then the lawyers arrived.
Less than a month after the breakup, Sperr says she received a letter titled “Maintenance Agreement.” By January 2025, the proposal appearing on paper had changed considerably.
The $50 million lump sum became $5 million a year for ten years. Ownership of a home became the right to live in one as a tenant. Support for her mother disappeared. A nondisclosure agreement appeared.
Sperr presents that progression as a promise being steadily reduced.
The documents may also become one of the most contested parts of the case. An offer made after a breakup does not necessarily prove what Bass promised when the relationship began ten years earlier. His lawyers could argue that the later proposal was simply an attempt to settle a separation, while Sperr can point to it as evidence that money, housing and long-term support had always been part of their arrangement.
That makes the paper trail important.
Certain long-term promises under New York law need written evidence, particularly agreements intended to last for life or involving ownership of real estate. Emails, estate documents and agreements could therefore end up carrying more weight than memories of conversations held years earlier.
The relationship had begun with Bass asking, “How about you never leave?”
It now reached the point where lawyers were trying to calculate what leaving was supposed to cost.
And Sperr says another woman was beginning to influence the answer.
The Art Adviser
According to the complaint, Althea Viafora Kress first approached Bass in late 2022 seeking advice about inherited money. Kress’s professional profile describes over 20 years of experience advising collectors, galleries, and artists, including her own gallery and advisory practice.
Sperr’s complaint portrays what followed as a calculated displacement.
The filing alleges that Kress positioned herself inside Bass’s inner circle during a period when his health was declining, his judgment was compromised by what the complaint describes as three mini-strokes, signs associated with Parkinson’s disease, and tremors worsened by heavy drinking, and his longtime partner could be pushed aside.
These are Sperr’s allegations, and they should be read as such. Parkinson’s doesn’t automatically produce incapacity, and influence isn’t automatically undue influence.
Bass was 82, not declared legally incompetent, and courts generally respect an adult’s right to change relationships however painful the consequences for those left behind.
And the complaint doesn’t ask the court to void the new marriage. It asks the court to enforce promises Bass allegedly made before Kress arrived.
The legal claims against Kress rest on a theory of tortious interference: that she knew about Bass’s promises to Sperr and intentionally caused him to break them.
If Sperr cannot first establish that a valid agreement with Bass existed, the interference claim against Kress collapses. If she can, she must then prove Kress knew its terms and deliberately caused the breach.
Neither Bass nor Kress has commented publicly on the substance of the complaint, and both are entitled to the presumption that the allegations against them are unproven.
Yet, before Sperr can prove that another woman interfered with Bass’s promise, she first has to prove there was a promise the law recognizes at all.
What The Future Holds
Whatever a court ultimately decides, the case raises a question that extends well beyond the Bass fortune.
When an unmarried partner sacrifices a career, manages a household, and organizes a decade of her life around promises made by someone with vastly more wealth and power, the law currently treats her as a contractor trying to prove a handshake deal rather than a spouse entitled to an equitable share.
Sperr’s $400 million complaint is, at its core, a test of whether that distinction reflects genuine legal principle or simply the gap between what wealthy men promise and what the system requires them to deliver.
Why would she give up her career to be a hospice care partner??? Why do women do this???
Unmarried partners promised anything should get it in writing or get paid-as-they-go! What is the point of raising a daughter with a pedigreed background if you aren't teaching her to care for herself first? While the patriarchy and the laws work against women often, women must shoulder some of the blame!