What to Know About Donald Trump's Niece Mary, Who Fought Him in Court & Is Writing a Tell-All

Twenty years ago, in what seems to have been her last major interview, Mary Trump had nothing nice to say about her uncle Donald Trump — or the rest of his siblings.

"My aunt and uncles should be ashamed of themselves," she told The New York Daily News in a December 2000 article. "I'm sure they are not."

Mary, then 35 years old and a graduate student living on Long Island, New York, was along with brother Fred Trump III fighting over grandfather Fred Trump Sr.'s will and a family policy about health coverage.

The legalistic issues belied the flesh-and-blood conflicts beneath, as recounted in the Daily News piece. Essentially, Mary and her brother said they had been swindled out of a fair share of Trump Sr.'s estate because his will left the bulk of it to his four living children, without an equal share to their late father, Fred Trump Jr., better known as Freddy.

"Given this family, it would be utterly naive to say it has nothing to do with money," Mary told the paper then.

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Decades later, Mary is set again to speak out about her family with a forthcoming tell-all, Too Much and Never Enough, according to a report in The Daily Beast. Publisher Simon & Schuster confirmed Monday the book will be released on July 28.

The Daily Beast described the book as including "harrowing and salacious" details.

It will also reveal how Mary "played a critical role" in The New York Times' reporting on her family's finances, according to the website — such as "supplying Fred Trump Sr.’s tax returns and other highly confidential family financial documentation to the paper."

If as described, the Trump family tell-all will be an explosive account from one of the president's own relatives, especially one so private.

Here's what else you need to know about his niece Mary.

Donald Trump/Instagram Donald Trump (left) as a boy with his family, in an undated photo

The five Trump siblings, including Donald Trump

She Hasn't Been in the Spotlight

As The Daily Beast notes, Mary "has kept out of the public eye and has not spoken publicly in decades." She was quoted in the Daily News article in 2000 about her family's legal fight but has scant appearances online or in the news.

Public records show she was born Mary Lea Trump in May 1965 and is 55 and lives on Long Island. Her publisher said she is a clinical psychologist and has a daughter.

She has one brother, Trump III. Both siblings were born to Trump Jr., President Trump's older brother, and Linda Trump, according to court papers. The couple divorced in 1970.

The Trump family has a history of successive generations named for the parents and grandparents before them: According to The New York Times, Mary's namesake is her father's mother.

As a girl, she was photographed in the Daily News along with her mother at a local hat show.

The Family Legal Battle Was Fierce

President Trump told the Times in 2016 that the 20-year-old fight in their family over his father's estate was "very amicably" settled. But the Daily News article from the time describes more intense emotions.

"You have to be tough in this family. I guess I have what my father didn't have. I will stick to my guns. I just think it was wrong," Trump III told the paper.

He was describing the most notorious part of the estate battle he, his sister, their mother and his wife were then fighting in New York.

After he and Mary sued in March 2000 alleging Trump Sr.'s will was "procured by fraud and undue influence" by their aunts and uncles — President Trump, brother Robert Trump and sisters Elizabeth and Maryanne Trump — the health insurance Trump III was using to pay for toddler son William's care was cut off.

Sonia Moskowitz/Getty From left: Donald Trump and Ivana Trump with his parents, Mary Trump and Fred Trump Sr., in May 1987 in New York City

"When [Trump III] sued us, we said, 'Why should we give him medical coverage?' " President Trump told the Daily News at the time.

"It's cold when someone sues my father. Had he come to see me, things could very possibly have been much different for them," he said of his nephew, who fired back: "These are not warm and fuzzy people. They never even came to see William in the hospital. Our family puts the 'fun' in dysfunctional."

Young William was born not long after Trump III spoke at the 1999 funeral for Trump Sr., but the little boy suffered serious health complications including seizures and cerebral palsy.

"We just don't know what William's future holds, what he will be able to do in his life," Trump III's wife, Lisa, told the Daily News.

The Conflict Over the Will

Mary told the Daily News in 2000 their issues were more personal than financial.

"For both me and my brother, it has much more to do with that our father [Freddy] be recognized," she said. "He existed, he lived, he was their oldest son."

"And William is my father's grandson," Mary continued. "He is as much a part of that family as anybody else. He desperately needs extra care."

Freddy, Trump Sr.'s oldest son and the president's older brother, died in 1981 when he was 42, after years of heavy drinking. Though never truly estranged, Freddy's failures in real estate and other personal troubles were a kind of black cloud in the family, which revolved around their property business.

When Trump Sr. died in 1999 after years with Alzheimer's, his will was clear, according to the Times: "It divided the bulk of the inheritance ... among his children and their descendants, 'other than my son Fred C. Trump Jr.' "

According to the Daily News, that meant that his grandchildren, including Mary and Trump III, each got $200,000 but their late father did not receive a share of the majority of Trump Sr.'s money, which instead was divided four ways to his surviving children.

While Mary and Trump III alleged some wrongdoing in the final version of the will, their aunts and uncles told a different story: President Trump, according to the Daily News, said they "lived like kings and queens" and aunt Maryanne said they were "absentee grandchildren."

"He had no intention of treating them as one of his children — none," Maryanne told the Daily News about her father's decision on inheritance.

Louis Liotta/New York Post Archives /(c) NYP Holdings, Inc. via Getty Fred Trump Jr. (left) in 1966

A judge ruled by the end of 2000 that the medical coverage the family had rescinded for Trump III continue "until the dispute is resolved," according to the Daily News.

Of the will's contentious four-way split, President Trump explained: "I think he [Trump Sr.] felt if it goes to the two children, it also maybe can go to the mother [Linda] indirectly. He felt the mother was the cause of some of Fred's difficulty, and Fred had a difficult life."

Speaking with the Times in 2016, the president said he "was angry because they sued." He said then that he had somewhat mended his relationship with Trump III, who the Times reported also worked in real estate.

Mary Has Reportedly Leaked About Her Family Before

In October 2018, the Times published a lengthy investigation of the Trumps' finances and reported that "[President Trump] received at least $413 million in today’s dollars from his father’s real estate empire, much of it through tax dodges in the 1990s."

(The president’s attorney claimed the reporting was “100 percent false.”)

According to The Daily Beast, Mary Trump was a key source and is ready to go public with her upcoming book, including describing "her involvement working with [Times] journalists ... to crack the story."

The website links the long-ago legal battle to the information Mary was reportedly able to hand over to the Times two years ago. Produced in that lawsuit was "a treasure trove of confidential and highly sensitive Trump family financial documents, including Fred Trump Sr.’s tax returns," according to The Daily Beast.

The Times did not respond to PEOPLE's request for comment, though a paper spokeswoman declined to comment for a Times article.

What Is in Her Tell-All

According to The Daily Beast, Mary's book will "include conversations with Trump’s sister, retired federal judge Maryanne Trump Barry, that contain intimate and damning thoughts about her brother" as well as a retelling of Freddy's death in '81.

Too Much and Never Enough, according to The Daily Beast, will include "allegations that Donald and Fred Trump Sr. contributed to [Trump Jr.'s] death and neglected him at critical stages of his addiction."

The president, who rarely speaks in personal terms, has repeatedly talked about the shadow of his older brother’s death and what role family influence may have played in his brother's problems.

“I do regret having put pressure on him,” he told the Washington Post last year. The family real estate business “was just not his thing … I think the mistake that we made was we assumed that everybody would like it.”

“He did [go to rehab]. A number of times,” the president told the paper then, noting that it was not a “stay-over” rehab. “I don’t think there was much we could do at the time. … Things have been studied and learned right now that are much different.”

The White House did not respond to PEOPLE's request for comment on Monday. Efforts to reach Mary were unsuccessful.