President Trump’s niece Mary Trump filed a lawsuit Thursday alleging that she was pushed out of the family business and that the president and his siblings cheated her out of tens of millions of dollars over the past several decades.

The lawsuit was filed in state court in New York City, seeking unspecified damages.

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“Fraud was not just the family business — it was a way of life,” the lawsuit stated.

The suit alleged that the president, his late brother Robert Trump, and a sister, former federal judge Maryanne Trump Barry, portrayed themselves as Mary Trump’s protectors, while secretly taking her share of interests in the family’s real estate holdings.

According to the suit, the president and his siblings devalued Mary Trump’s interests, which included a share of hundreds of New York City apartments, by millions of dollars, even before Donald Trump’s father, Fred Trump Sr., died in 1999.

After his death, Mary Trump and her brother filed objections to the will, according to the suit, and the president and his siblings “ratcheted up the pressure” to settle by cutting off health insurance to them. The suit described the action as “unfathomable cruelty.”

Meanwhile, the suit stated that the Trump family provided fraudulent accounting and financial statements that misrepresented the value of Fred Trump Sr.’s estate at $30 million or less, as they pressured Mary Trump to accept a settlement.

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“In reality, Mary’s interests were worth tens of millions of dollars more than what Defendants represented to her and what she received,” the lawsuit stated.

Mary Trump’s lawyers did not say how much she ultimately received, citing the confidentiality clause in a settlement of the dispute over Fred Trump Sr.’s will, but based on the numbers provided in the lawsuit, it appeared unlikely that she would have received more than several million dollars.

The lawsuit comes after Mary Trump published a tell-all memoir, “Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man.” The book hit shelves on July 14.

Prior to the release of the book, the president’s brother, Robert Trump, who passed away last month, filed a lawsuit requesting a preliminary injunction and temporary restraining order to prevent the book from coming out.

Robert Trump had claimed Mary Trump was barred from writing about private family affairs because of a non-disclosure agreement she signed as part of a settlement over her inheritance.

The book highlighted “how Donald [Trump] acquired twisted behaviors and values,” including that “financial worth is the same as self-worth; humans are only valued in monetary terms,” that “taking responsibility for your failures is discouraged,” and “cheating as a way of life.”

“In addition to the firsthand accounts I can give as my father’s daughter and my uncle’s only niece, I have the perspective of a trained clinical psychologist,” Mary Trump wrote in the prologue. “'Too Much and Never Enough' is the story of the most visible and powerful family in the world. And I am the only Trump who is willing to tell it.”

Fox News' Maria Patronich and the Associated Press contributed to this report.