Michael D'Antonio is the author of the book " Never Enough: Donald Trump and the Pursuit of Success " (St. Martin's Press). The opinions expressed in this commentary are his.

(CNN) Donald Trump Jr. has become a prime target for the House and Senate intelligence committees, Special Counsel Robert Mueller and an army of journalists who are all investigating Russia's efforts to sway the 2016 election in his father's favor.

By releasing emails related to his encounter with a Russian lawyer in the summer of 2016, Donald Jr. has potentially undermined the White House's claim that no one in the President's campaign collaborated with Russia in its efforts to influence the US election.

So far, the Trump family is standing by Donald Jr. The President praised him for his transparency in a one-sentence public statement on Wednesday, before reiterating his support on Twitter. Then Eric Trump, his younger brother, tweeted in response , "This is the EXACT reason they viciously attack our family! They can't stand that we are extremely close and will ALWAYS support each other."

And while it seems the Trump family remains quite loyal to one another, the question remains: will they always be, particularly to Donald Jr., who hasn't always enjoyed the benefits of the family name?

He delayed joining the family firm after college, and when his father became President, he was left behind in New York while his sister Ivanka and brother-in-law Jared Kushner were ensconced in the White House. Additionally, it might have been Kushner's failure to disclose this meeting with the Russian lawyer when he applied for security clearance that led his attorneys to amend the application, and that led the story, implicating Donald Jr., to go public.

As I learned in interviews with all three elder Trump children, Donald Jr. was the Trump child most reluctant to join the enterprise built around his father's personality.

One of the defining events of Donald Jr.'s early life was the sex scandal that led to his parents' divorce. Ivana, the President's first wife and mother of his three eldest children, had discovered her husband's relationship with a young model/aspiring actress named Marla Maples. In the months after she confronted him, the Trumps waged a war of lurid headlines in the New York tabloids. Donald Jr., Ivanka and Eric were caught in the crossfire. As the eldest, 12-year-old Donald Jr. may have suffered the most.

All of the Trump kids credit their mother with being the strongest influence in their early lives. When I interviewed them in 2014, they described their father as caring but aloof -- not one for attending ballet recitals or playing ball. Donald Jr. was especially close to his mother and her family. Starting at the age of five, he spent summers with her parents in what was then Czechoslovakia, and his face brightened when he talked about his Czech grandfather who "took me fishing, and taught me to shoot a bow, and BB guns."

The Trump divorce "was on the cover of every paper in the city for years," Donald Jr. told me in 2014. "(I was) not quite a boy, not quite a man, so for me it was kind of like, 'I should probably get out of New York City.'" He escaped to a boarding school where he was happy to discover that many of his peers didn't care about his last name.

According to New York Magazine, in college, he was the wild child of the clan who drank too much and wasn't so sure he wanted what waited for him in the family business. After graduation, he chose bartending in Colorado over a job with the Trump Organization and spent 18 months weighing his options.

Donald Jr. would have risked becoming a complete outsider had he not accepted an executive position as a vice president in the Trump Organization. Instead, he settled into the fold, marrying, having five children and accepting the scrutiny that comes with being a Trump heir. In his professional role, he has sometimes played the heavy, as he did with locals in Scotland who opposed the family's development of a golf course there.

Ivanka and Eric, neither of whom expressed any doubts about becoming part of the family firm, also joined the company but have never been required to act tough in a way that anyone noticed.

Although a cardinal rule of parenting prohibits choosing a favorite, every avid Trump-watcher knows that Ivanka is the apple of her father's eye. Gifted with natural poise, she was a teenage fashion model, and, as an adult, she has poured herself into the role of representing the softer side of the family brand.

"I have always had really big aspirations," Ivanka once told me. She also said that she believes the Trump name and resources have given her the means to pursue those aspirations. Ivanka added to the gleam in her father's approving eyes when she married real estate magnate Jared Kushner, who would become vital to the President's political campaign, and who now, like his wife, has an office in the White House.

While Ivanka gracefully adapted to a very public role, Eric Trump, the youngest and least well-known of Donald and Ivana Trump's children, has been slow to make his mark. Naturally quieter, he has generally avoided controversy and favored lower-profile projects, like a Trump-branded winery and charitable activities.

Like his brother and sister, Eric was raised in a fun house mirror environment where their father played games with the press in order to attract notoriety, and where family legends, such as the one about their mom being an Olympic skier , were built on half-truths. (She was a great skier. She was never an Olympian.) All young adults must sort family fictions from facts. In the case of the Trumps, the task came with the added burden of a father who is a master mythmaker.

Once alienated from his father, Donald Jr. was the one who had the most to prove when he accepted his position in the Trump family business. In business and then in politics, he has shown he is willing to be aggressive in a manner similar to his father's, but he hasn't shown himself to be as shrewd. This may explain why he got cornered by the Russia controversy. Unlike his father, who always leaves himself a way out of a trap, Donald Jr. is ensnared.

In the one interview he has given on the subject, Donald Jr. told Sean Hannity of Fox News that, at the time of the meeting with the Russian lawyer, he was still a political neophyte. "This is the first time we've ever done any of this," he said, referring to the campaign. "This is -- you know, I'm still way in the learning curve on all of this." At another point in the program he told Hannity, "In retrospect, I probably would have done things a little differently."

Although he is caught in trouble of his own making -- he did previously deny the Trump team's involvement with Russians -- the President's son might also be seen as a man who is unsuited to the role he felt he could not refuse.

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Considering this prospect, I cannot help but recall the man whose eyes lit up when he spoke to life outside the Trump machine. "When I'm at my cabin in the Catskills in the weekend, a lot of the guys that are local up there, they know me as Don, the good fly fisherman," he said.

I'm guessing that, right now, he's thinking a lot about how much he prefers a trout stream to the political hot water rising around him.