Donald Trump Jr.'s sometimes-strained relationship with President Trump faces new scrutiny

Trump Jr. is President Trump's eldest child from the first of three marriages.

He continued, “I'd go, say, introduce myself as just Don, or sometimes I'd avoid the last name at all.”

Trump Jr. did not join the Trump family’s real estate business immediately after graduating from his father’s alma mater, The Wharton School at the University of Pennsylvania.

"I think, like anyone else, I made my mistakes,” Trump Jr. told The New York Times this year about his arrest, for which he reportedly spent 11 hours in jail. “We have to be honest with ourselves. I’m not good at it, moderation. You have to have the conversation, be a realist, and say, ‘I guess I’m not doing myself any favors.’”

Trump Jr. also reportedly did not speak to his father for a year after now-President Trump separated from his mother, Ivana Trump, who is also the mother of Ivanka Trump and Eric Trump. Their parents’ divorce, which made the front pages of tabloids, came when Trump Jr. was just 12.

Trump Jr., now executive vice president of The Trump Organization, gave an insight into working with his dad while discussing now-President Trump’s signature "Apprentice" tagline of “You’re fired," in an interview with ABC News’ Tom Llamas last month.

“Before ‘The Apprentice’ and the ‘You're fired’ thing ever was a thing, he used to say that. Which was, you know, ‘If you don't do a good job, I'll fire you like a dog,’” Trump Jr. said. “And, you know what? He meant it.”

Trump Jr. met his wife, Vanessa Haydon Trump, a former model, through his father and married her in 2005. The couple, who live in New York City, have five young children.

Trump Jr. has sparked outrage with his hunting exploits, most notably when photos surfaced in 2012 from a hunting trip with his brother Eric Trump in Zimbabwe that showed Trump Jr. wearing an ammunition belt and posing with a dead buffalo in one photo, and holding the tail of an elephant in another photo.

Hunting though helped Trump Jr. connect with conservative voters across the country as he became one of his father’s biggest surrogates during the 2016 campaign.

Now that Trump Jr. is embroiled in the investigation into Russian collusion -- which he called a “witch hunt” as recently as last month -- it is his father who is speaking out in defense of the son.

In a statement Tuesday, the president said, “My son is a high-quality person, and I applaud his transparency.”

Trump also took to Twitter today to praise his son for being “open” and “transparent” after Trump Jr. tweeted four pages from what he said is an email chain documenting the planning of the 2016 Trump Tower meeting with lawyer Natalia Veselnitskaya.

Trump Jr. told ABC News' Tom Llamas in June that he and President Trump barely speak now that he is in the White House because he knows how busy his father is.

He also added that President Trump called three times a day recently when one of Trump Jr.'s children was recovering from an injury.