Mary Trump writes in Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man that his upbringing in the wealthy real estate family led him to develop “twisted behaviours”.
Ms Trump, estranged from the president for many years, faced a legal challenge from the Trump family to halt publication of the book, but a New York judge saw no reason to do so.
The tell-all book by President Donald Trump’s niece depicts a family riven by greed and betrayal over generations that turned him into “the world’s most dangerous man”.
Excerpts of the book, due to be released next week, say that the president went to see a movie while his brother was dying in hospital, and paid someone to take his college entrance exams.
A separate ruling is expected soon on whether she violated a 20-year-old confidentiality agreement.
In the memoir Ms Trump says that her uncle sees “cheating as a way of life”. While at high school in Queens, she alleges that he paid someone to take the SATs on his behalf. The president went to Fordham University before transferring to Wharton business school at the University of Pennsylvania.
A particularly damning revelation concerns the death of Fred Trump Jr, the eldest son, known as Freddy and considered the black sheep of the family. He was also Mary’s father.
Having endured a miserable time working for the family real estate business under his father, Fred Trump Sr, Freddy pursued a career as a pilot for Trans World Airlines.
A heavy drinker, he died in 1981 from an alcohol-induced heart attack aged 42. On the night he died, she says that the family sent him to the hospital alone. She also writes that Donald went to see a movie.
After the death of her father, the family helped support both Mary and her brother, Fred III.
Not all of the alleged revelations take place as long ago. Ms Trump writes that Donald’s sister, Maryanne Trump Barry, questioned his fitness for office after he announced he was running for president.
The retired federal appeals court judge apparently said to Mary in 2015: “He’s a clown — this will never happen.”
Further to that, Mary said her aunt couldn’t understand evangelical Christians giving their support to her brother’s campaign.
“The only time Donald went to church was when the cameras were there,” she reportedly said.
“It’s mind boggling. But that’s all about his base. He has no principles. None!” she added.
Ms Trump became estranged from Donald after the death of Fred Sr in 1999. Both she and her brother contested his will, having expected to receive a portion of his estate equal to what her father would have received were he alive.
A settlement was eventually agreed between the siblings and their uncles and aunt, that also involved them signing the aforementioned confidentiality agreement.
As a clinical psychologist, Mary Trump states in the book that her uncle, the president, has all nine of the clinical criteria displayed by narcissists.
Further, she says that his psychological troubles go even beyond that diagnosis and that his “pathologies are so complex and his behaviours so often inexplicable that coming up with an accurate and comprehensive diagnosis would require a full battery of psychological and neuro-physical tests that he’ll never sit for”.
Ms Trump lays the blame at the feet of her grandfather, Fred Sr, whose domineering manner and treatment of his oldest son, affected the president’s emotional development and “perverted his son’s perception of the world and damaged his ability to live in it.”