Trump is reportedly looking into suing his niece to stop her from publishing a tell-all book about him

• President Donald Trump is looking into whether he can sue his niece to stop her from publishing a tell-all book about him, The Daily Beast reported Tuesday, citing sources.
• News broke over the weekend that Mary L. Trump is publishing a book about her uncle, titled "Too Much and Never Enough: How My Family Created the World's Most Dangerous Man."
• In the book, Mary Trump will reportedly reveal herself as the source of a New York Times investigation into Trump's finances, and say that Donald Trump mocked his father as he succumbed to Alzheimer's.
• According to The Daily Beast, Mary Trump signed a non-disclosure agreement in 2001, when she and her uncle reached a settlement concerning her inheritance, which bars her from publishing anything about her relationship with her uncles and aunt.

President Donald Trump is looking into suing his niece to stop her from publishing a critical tell-all book about him, The Daily Beast reported Tuesday, citing sources with the matter.

Simon & Schuster plan to release Mary L. Trump's "Too Much and Never Enough: How My Family Created the World's Most Dangerous Man" on July 28.

The president has told people close to him that he's having his lawyers look into what they can do to legally threaten his niece over the book, two people familiar with the matter told The Daily Beast.

The outlet said this would "likely" be "in the form of a cease and desist letter."

One of the sources said that the president mentioned at one point that Mary had signed a non-disclosure agreement years ago.

Sources familiar with the matter told the Daily Beast that Mary signed an NDA in 2001, when she and her brother, Fred Trump III, came to a settlement with her uncle and two of his siblings over Fred Trump Sr.'s estate.

The NDA reportedly barred her from publishing anything regarding the litigation and her relationship with Donald Trump, Robert Trump, or Maryanne Trump Barry — who acted as executors of their father's estate.

The bad blood between Mary Trump and her uncle appears to date back to this legal case, details of which were publicized at the time in a New York Daily News article.

Mary Trump is the daughter of Fred Trump Jr., Donald Trump's older brother who died at the age of 42 in 1981 due to complications from alcoholism.

Mary Trump and her brother took issue with the fact that they didn't receive what would have been their father's share of their grandfather's estate when the latter died in 1999. Instead, most of Fred Sr.'s wealth was divided between his surviving four children.

When Fred Jr.'s children contested the will, Donald Trump responded by cutting them off the family's healthcare plan. This was an especially tough blow for Fred III, who had just welcomed a baby boy with serious health issues.

The case was settled the next year, and details of the deal were never released — but not before Mary Trump bashed her aunt and uncles to the Daily News in December 2000, saying they "should be ashamed of themselves."

According to a previous Daily Beast report, Mary Trump will out herself in the book as the primary source for the New York Times' 2018 exposé on Trump's finances, by saying that she supplied the outlet with confidential financial documents. The Times declined to comment on this claim.

A description of the book on Simon & Schuster's website, published Monday, also reveals other details of the book — including how the president reportedly mocked his father when he began to succumb to Alzheimer's disease in the 1990s.

Neither the White House nor Simon & Schuster immediately responded to Insider's request for comment.

Trump is no stranger to suing people trying to publish critical books about him. The Trump administration this week sued former national security adviser John Bolton to stop him from publishing his new book, accusing him of breaching his contract and compromising national security.

• Read more:
• Trump's niece is publishing a tell-all book that says she leaked tax documents to help The New York Times investigate the president's finances
• Trump mocked his father as he started succumbing to Alzheimer's, according to his niece's upcoming tell-all
• Trump in new interview admits 'regret' over how he treated his late brother Fred Trump Jr., who struggled with alcoholism
• Trump says his father was 'born in a very wonderful place in Germany' — but Fred Trump was actually born in New York City