The presumptive Republican nominee's search for a running mate revealed the intense and increasing role of three of his adult children, Donald Jr., Eric and Ivanka Trump, along with his son-in-law Jared Kushner, in the billionaire's unorthodox political operation.

Trump offered the vice presidential slot to Indiana Gov. Mike Pence Wednesday, CNN has learned, and the Indiana governor accepted. Sources said that Trump's decision to pick Pence over more controversial candidates such as New Jersey Gov. Chris Christie followed a sustained behind-the-scenes lobbying push orchestrated from within the family's inner circle.

After building a presidential campaign almost exclusively on the strength of his own persona and often seeming to make decisions on the fly, Trump's willingness to listen to others while agonizing over his most important political move yet does not just suggest a candidate who is evolving politically. It shows a man who is not used to being told he is wrong and who makes an exception for the opinions of those who are his own flesh-and-blood.

"I think he has developed a level of trust in us that would be very hard for most people who came into a campaign seven months ago to replicate," Eric Trump said in an interview with Time Magazine published Thursday.

Lacking a traditional campaign operation, ties with the GOP establishment and the desire to pay millions of dollars to political consultants, Trump has, in effect, morphed his corporate operations, in which his children play substantive leadership roles, into a small but intensely loyal political kitchen cabinet.

That has meant investing Eric and Donald Jr. and Ivanka, his children with his first wife Ivana Trump, with considerable power in his campaign.

While Trump has parted with long-term advisers such as Roger Stone and former campaign manager Corey Lewandowski, his family has consolidated power and laid the foundations for increased influence.

Michael D'Antonio, who wrote a biography of Trump, told CNN's Brooke Baldwin Thursday that Trump's children were "supremely" important to their father's political and businesses careers.

"These are people who have his back and they have always protected him -- especially the three adult children," said D'Antonio on "Newsroom" with Brooke Baldwin.

"They actually told me they will get together and if they think their father is off on the wrong track, as a group they will sit with him," D'Antonio said, though cautioned that the billionaire did not always take his children's advice.

"They will rein him in and protect him from himself," he said.

The circus surrounding Trump's vice presidential selection process was a study of just how much leverage those closest to him exert.

At the crucial moments, when Trump was narrowing in on his choice of a vice presidential pick, his family was by his side. And sources say they may have convinced him to go with Pence rather than making a "gut" level call to choose Christie or Gingrich.

After Trump stayed overnight Tuesday into Wednesday in Indiana because of a plane malfunction, the Trump siblings made a snap decision to fly out out to be with their father, as he met Pence on Wednesday morning for breakfast, after auditioning the Indiana governor for his presidential ticket at a rally the night before, sources told CNN's Dana Bash.

They were worried that their father was torn and unsure about what to do and was maybe leaning in a direction they didn't favor.

Other sources suggested that while the family inner circle might at one point have been also favoring Gingrich, the children warmed toward Pence after spending time with him in the Hoosier state.

After a gilded childhood and the best schooling money can buy, the Trump siblings spent years increasing their clout in various branches of his corporate empire. Eric Trump, for instance, now runs his father's golf and construction empire -- the presumptive nominee's trip to a reopened golf resort in Turnberry, Scotland last month, was ostensibly to honor his son's work.

Ivanka Trump, whose polished and refined persona contrasts with that of her brash father has masterminded the conversion of the Old Post Office building in Washington into a high-end hotel, a project about which Trump proudly boasts repeatedly in his stump speech.

Trump's pride in his offspring is evident -- he brags on them in almost every campaign speech -- and he clearly sees their success as a reflection of himself. For instance, he declared at a rally in Cincinnati last week that "everyone loves Ivanka." And he said Eric was doing a "damn good job."

"I think I've been a good father, and I want to support them," he said.

Now, the apprenticeships served in Trump Inc. have morphed into major new roles for the kids, who are trying on new hats as campaign strategists and behind-the-scenes players in the Trump political project.

The increasing power the Trump siblings wield inside their father's political orbit also suggests that if the billionaire wins the election in November, his family would become a power behind the throne in his White House as well.

According to Time , Donald Jr. dreams of a job in the administration itself as interior secretary but has yet to convince his father, who expects his children to run his business if he becomes president, it's a good idea.

Kushner, meanwhile, has become an increasingly important political influence on Trump. When the billionaire was accused of using Star of David imagery in an attack on Democratic presumptive nominee Hillary Clinton, Kushner, who is Jewish, came to his father-in-law's defense, writing in the New York Observer , a newspaper he owns, that Trump "is not an anti-Semite."

It's not unheard of for a potential president's closest family members to emerge as their most trusted counselors during the long climb to power.

No one for instance, was closer to John F. Kennedy than his brother Robert -- who went on to serve in his administration as attorney general. And Hillary Clinton was a driving force in President Bill Clinton's rise -- and later took on an ill-fated role in the administration shepherding health care reform.

But the speed with which the Trump family troika has built its political powerbase during their father's campaign has been remarkable -- and may partly be a reflection of the fact that Trump, who ran an outsider primary campaign that shredded the Republican establishment, has few real friends in politics.

"Don't underestimate the importance of his children's opinions," a Trump source told CNN's Gloria Borger, as the billionaire agonized this week over the choice of his running mate.

Eric, Donald Jr. and Ivanka will all deliver speeches at the Republican National Convention in Cleveland next week, as well as Trump's daughter from his marriage to Marla Maples, Tiffany.

His children's appearances will combine the traditional role of a candidate's family in offering testimony to a nominee's character, with that of high-profile influencers of the campaign's direction.

There is no word on a campaign role for Trump's youngest child -- Barron -- who he had with his third wife, Melania. But if the past is any guide, it won't be long before he too carves out a role in the Trump empire.

"Barron has great potential but he's 10," Trump mused in Cincinnati. "But he's got great potential."