President Donald Trump's brother, Robert Trump, has gone to court in an attempt to stop his niece Mary Trump from publishing a family tell-all book, multiple reports said Tuesday.

Mary Trump is the daughter of Fred Trump Jr., the president's older brother, who died in 1981. Her book is titled “Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man."

The book is set to be published July 28 by Simon & Schuster, with a description saying she "shines a bright light on the dark history of their family in order to explain how her uncle became the man who now threatens the world’s health, economic security, and social fabric."

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President Donald Trump speaks at the Students for Trump conference at Dream City Church, Tuesday, June 23, 2020, in Phoenix. (Associated Press)

The motion, filed by Robert Trump's lawyers, seeks an injunction to prevent Mary Trump and the publishing company from releasing the book. They argue that family members had signed a settlement agreement two decades ago related to the will of Donald Trump’s father, New York real estate developer Fred Trump. The agreement included a confidentially clause saying they would not "publish any account concerning the litigation or their relationship,” unless agreed upon by all parties.

Robert Trump said he never consented to the book being published and argued it was prohibited by the accord reached in 2001.

“President Trump and his siblings are seeking to suppress a book that will discuss matters of utmost public importance," attorney Theodore Boutrous Jr., a representative for Mary Trump, said in a statement. "They are pursuing this unlawful prior restraint because they do not want the American people to know the truth. The courts will not tolerate this brazen and baseless effort to squelch speech in violation of the First Amendment.”

President Trump previously said during an interview last week that Mary Trump is "not allowed" to write the book due to the nondisclosure agreement she signed.

"She's not allowed to write a book," Trump told Axios. "You know, when we settled with her and her brother, who I do have a good relationship with — she's got a brother, Fred, who I do have a good relationship with, but when we settled, she has a total ... signed a nondisclosure."

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A Simon & Schuster official said in a statement he was confident the attempt to block publication would fail.

“Mary Trump has written a compelling personal story of worldwide significance, and we look forward to helping her tell her story,” said Adam Rothberg, spokesman for the publishing house.

"She describes a nightmare of traumas, destructive relationships, and a tragic combination of neglect and abuse," according to the book's description on Simon & Schuster's website. "She explains how specific events and general family patterns created the damaged man who currently occupies the Oval Office, including the strange and harmful relationship between Fred Trump and his two oldest sons, Fred Jr., and Donald."

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The legal battle comes as President Trump fought off reported excerpts from former national security adviser John Bolton’s book before its release Tuesday and as reporter Bob Woodward is set to publish a follow-up to his first book on Trump's administration.

Fox News' Brie Stimson and the Associated Press contributed to this report