According to a new book written by Pulitzer Prize-winning Washington Post reporter Carol Leonnig, Secret Service agents are not allowed to date the people they're guarding, but the agency did not object to Vanessa Trump, Mr Trump Jr's ex-wife, entering into a relationship with the agent because he was no longer assigned to protect her after the divorce.
The Guardian obtained a copy of the book and reported the findings.
Apparently Vanessa Trump was not the only member of the Trump clan to become romantically entangled with a Secret Service agent.
The book – "Zero Fail: The Rise and Fall of the Secret Service" – also reports that there were suspicions that the former president's daughter, Tiffany, also may have formed a relationship with a Secret Service agent.
Ms Leonning claims in the book that Tiffany Trump broke up with her boyfriend and "began spending an unusual amount of time alone with a Secret Service agent on her detail," which apparently caused some concern among agency leaders, who became "concerned at how close Tiffany appeared to be getting to the tall, dark and handsome agent."
Neither Tiffany Trump nor the agent have spoken about anything out of line occurring, Ms Leonning wrote, and included that the agents often do have to spend time alone with the individuals they are guarding.
The agent was reassigned after concerns were raised.
The Trumps sometimes had strange and contentious relationship with the Secret Service agents.
Donald Trump reportedly asked for overweight agents or agents he deemed "too short" to be removed from his detail.
“I want these fat guys off my detail,” Mr Trump reportedly said, according to the book. “How are they going to protect me and my family if they can’t run down the street?”
The former president may have been confusing office personnel with field agents, who have different fitness requirements.
In January it was reported that Ivanka Trump and Jared Kushner banned Secret Service agents from using any of the half-dozen bathrooms in their Washington DC home, forcing the agents to seek out porta-potties or the bathrooms at the homes of former president Barack Obama and Vice President Mike Pence when they needed to use the facilities.
The agents eventually rented a $3,000 per month apartment across the street from the home of the president's daughter just to use a bathroom.
The White House at the time denied the claims and said the Secret Service chose to rent the home on its own.
After the story broke, the Secret Service sent news outlets an email explaining that it tried not to impose on private residences by using bathrooms and corroborated the White House's version of events.
"Ivanka Trump and Jared Kushner have not denied Secret Service personnel access to their home to include use of the restroom,” the email said.
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