Washington (CNN) The week after a parade of Cabinet-level officials released statements denying their involvement in an anonymous New York Times op-ed attributed to a Trump administration official, a high-profile surrogate made an appearance on a network morning show to defend the President: his eldest son.

Calling the anonymous writer's screed "disgusting" and "pretty sad," Donald Trump Jr. told ABC's "Good Morning America" that the circle of trusted aides within the West Wing walls is shrinking.

"I think there are people in there he can trust. It's a much smaller group," Trump said in an interview that aired Tuesday morning.

In a White House where the loyalty of some is in question, family members are among the very few Trump trusts completely.

Trump Jr., the President's eldest son, remains his father's most vocal advocate among the Trump family, imitating the hard-charging style of his Twitter account in his occasional television appearances acting as a staunch defender.

Likely the most ideologically conservative of his siblings, Trump Jr. grew up reading conservative books, listening to conservative radio and consuming conservative media well before his father formally entered the political arena.

He's also a lifelong outdoorsman, having learned to hunt and fish from his Czech grandparents, Ivanka Trump wrote in 2010. He participated in multiple hunting outings during the 2016 campaign, including in Iowa the week before the caucuses, and has long been outspoken in his Second Amendment support.

"He really believes this stuff and has, long before his dad got involved in politics," a source close to Trump Jr. told CNN.

Trump Jr. is an effective surrogate because he "understands the conservative id," the source close to the President's son said.

"He comes to politics already being into it and already understanding conservative politics. And he does have a natural ability on the stump. He knows how to electrify a crowd, he's got a good deal of natural charisma. And because he understands the conservative id, he knows what issues to raise to excite the audience," the source said.

By remaining in the private sector, Trump Jr. is also unburdened by the constraints of the White House.

He answers to no one, and in turn, has the freedom and flexibility to speak out publicly in ways administration staffers can't -- or won't. And he has the unique relationship among his siblings of being the oldest son, which comes with its own set of responsibilities, expectations, and need to please.

Parents' divorce

Trump Jr. has had a complicated relationship with his namesake; he was 12 when his parents' high-profile, messy divorce was splashed across the New York tabloids. Trump Jr. was devastated, according to accounts in Vanity Fair and New York Magazine

"How can you say you love us? You don't love us! You don't even love yourself. You just love your money," the young Trump Jr. told his father, according to friends of Ivana Trump, cited in a 1990 Vanity Fair report

He didn't speak to his father for a year, he told New York Magazine

"Listen, it's tough to be a 12-year-old," Trump Jr., then 26, told the magazine in the 2004 profile, which also featured his siblings.

"You're not quite a man, but you think you are. You think you know everything. Being driven into school every day and you see the front page and it's divorce! THE BEST SEX I EVER HAD! And you don't even know what that means," he told the magazine. "At that age, kids are naturally cruel. Your private life becomes very public, and I didn't have anything to do with it: My parents did."

Trump Jr. was more charitable during the 2016 presidential campaign. He told CNN's Anderson Cooper during an April 2016 town hall that the divorce was "a difficult thing" but said his father has "always been there."

"I think throughout our lives, he's always been there. It's usually been on his terms. It wasn't a typical 'let's go play catch in the backyard' sort of father/son relationship," Trump Jr. told Cooper. "But we always went to job sites with him. We'd be in his office playing with trucks as a 6-year-old while he's negotiating deals with presidents of major companies."

More than a decade later, the hard-charging, no-apologies eldest child of Donald Trump found himself his father's most visible and outspoken 2016 campaign surrogate, criss-crossing the country.

The two now appear to share a warm relationship. Trump Jr., along with his brother, Eric, took the reins of the family real estate business when their father assumed office.

The siblings

In the immediate aftermath of the divorce, Trump Jr.'s sister, Ivanka, became closer to her father, she wrote in her 2010 book

"I went down to see him every morning before school, and I also started dropping by his office on my way home in the afternoon. Just to say hello. In no hurry to get back to whatever I'd been doing, because nothing was more important," she said in "The Trump Card."

"Not incidentally, all that time in my father's office was well spent. I went to hang out and spend time with him, but I couldn't help but soak up a thing or two about business," she wrote.

That bond between Trump and his daughter has now made its way to the White House, where she serves as an adviser.

Unlike her eldest brother, Ivanka Trump has sought more common ground with her politics. But she has widely embraced some of the administration's conservative policies, notably working with Republicans on Capitol Hill on tax reform. She donated to Democratic causes as recently as 2014

Their younger brother, Eric Trump, was also on the 2016 campaign trail and continues to be active in midterm and re-election campaign strategy. His wife, Lara, who has a background in television production, serves as a senior adviser to the campaign. Eric Trump appears occasionally on Fox News but is generally less active on social media and network television than Trump Jr.

Youngest sister, Tiffany, Trump's daughter with Marla Maples, is a second-year student at Georgetown Law. And youngest brother Barron Trump, 12, lives in the White House but has been shielded from the political fray.

Twitter strategy

Not unlike his father -- or, perhaps, modeled after -- Donald Trump Jr. has emerged as a megaphone for many in the conservative right through his social media use.

Trump Jr. frequently employs his Twitter account to hit social media companies for censorship of conservative voices, pointing attention toward Hillary Clinton's emails, propagating attacks on news sources he deems as "fake news," retweeting conspiracy theories about the deep state, and calling out what he perceives as bias against his father's administration.

He has also been criticized for inflaming racial tensions over his father's proposed immigration policies via social media.

The message sometimes gets repeated by his father, who follows just 47 accounts, including his son's.

For instance, Trump Jr. has tweeted and retweeted multiple times about " Big Tech's " censorship of conservative media.

This week, Trump Jr. punched back at a Vanity Fair report that claimed he was concerned his father wasn't sleeping.

"What a joke, you think I worry my father isn't sleeping? I have never and will never worry about that. Keep making crap up," he tweeted, tweaking the magazine for its retweet to follower ratio.

"SAD, PATHETIC, & IRRELEVANT!" he wrote.

What a joke, you think I worry my father isn't sleeping?🤣🤣🤣 I have never and will never worry about that. Keep making crap up.



Oh, VF with 4.8m "followers" how do you average less than 20 RTs for your last 20 or so posts? BUYING FOLLOWERS MUCH? SAD, PATHETIC, & IRRELEVANT! https://t.co/hAhNAl88KL — Donald Trump Jr. (@DonaldJTrumpJr) September 14, 2018

Despite the fact that he aggressively counter-punches via social media, the father of five says that demeanor is separate from his private life. He separates that public persona from his more even-keeled disposition.

"I'd like to be more like him when it comes to business -- but I think I'm such a different person, it's hard to even compare us. His work persona is kind of what he is. I have a work face, and then there's my private life," he told New York Magazine in 2004.

Trump Jr.'s wife, Vanessa, filed for divorce earlier this year. He is currently dating Kimberly Guilfoyle, a Fox News anchor-turned-vice chairwoman of a Trump-aligned super PAC.

Don Jr. these days

JUST WATCHED What we know about the 2016 Trump Tower meeting Replay More Videos ... MUST WATCH What we know about the 2016 Trump Tower meeting 01:22

Donald Trump Jr. was thrust into the spotlight last year amid Robert Mueller's investigation into Russian meddling in the election for his involvement in a June 9, 2016, meeting where he was promised dirt on the Clinton campaign.

Just before The New York Times published a report on them, he proactively made public the emails he exchanged with Rob Goldstone, a publicist who arranged the meeting, via Twitter in July 2017.

Trump Jr. was promised "official documents and information that would incriminate Hillary and her dealings with Russia" that was "part of Russia and its government's support for Mr. Trump."

"If it's what you say I love it," Trump Jr. replied in an email to Goldstone, who represents the son of an Azerbaijani-Russian businessman close to the Russian government.

Trump Jr. has since testified before the Senate Judiciary Committee over the matter.

Asked by ABC Tuesday whether he's afraid he could go to jail, Trump Jr. said: "I'm not because I know what I did and I'm not worried about any of that. That doesn't mean they won't try to create something but, again, I'm not."

The scrutiny of the investigation has not yet deterred Trump Jr. from maintaining a robust schedule of public appearances on the 2018 campaign trail, where he continues to serve as a leading surrogate. In the coming days and weeks, he has appearances scheduled alongside candidates in Ohio, Pennsylvania, North Dakota and Texas.