When Owen Brennan and his wife emigrated from Roscommon in the west of Ireland last century, they never dreamed  their son would become the key figure in America’s national security and right hand man to President Barack Obama.

Rising from the ranks of the CIA, John Brennan now sits as overseer of Homeland Security and Counterterrorism since May 2009. In effect, he is America’s terrorism czar.

Brennan has become Obama’s go-to guy on national security. They talk and meet several times a day, and the workaholic Brennan is never far from the president’s side at home or abroad.

A senior member of Congress who deals with intelligence issues described him to Time magazine as “the president’s guy.”

"It's very ironic that a guy who they thought could not get confirmed as CIA director and who they stuck in a windowless room in the White House basement has all the power," added the member, referring to Brennan’s withdrawal from the position of CIA Director.

Brennan still pays homage to his Irish roots, is a regular at the White House St. Patrick’s Day party, and has visited the old homeland on several occasions.

A New Jersey native, Brennan followed the well-worn Irish Catholic path, graduating from Fordham University in 1977, a period which included a study abroad program in Cairo.  He went on to earn an MA from the University of Texas before he joined the CIA as an intelligence director in 1980.

On any given day, Brennan will receive countless terror alerts on every range of threat. He constantly receives alerts about suspicious airline passengers.

"We had a couple this morning," Brennan told Time.

"Is this just an inebriated passenger? You're trying to make sure that you understand the nature of the threat."

Right now the top priority for Brennan is the continued threat of radical Islam. The 55-year-old realizes if terrorists strike, he will be the first one to be interrogated.

"Next time something happens, I'm sure I'm going to be blamed by some of the folks in Congress [who will say] that, you know, we didn't do enough," he says.

A fluent Arabic speaker, Brennan is proud of how the Obama administration has put an end to Bush era-policies such as water boarding and secret prisons, which he describes as "a way to signal to the world that America is a country of values.”

In 1999, Brennan was appointed CIA Director George Tenet's chief of staff, a role which has greatly benefited him in his current position.

"I can't tell you how important it is to have someone at the White House who understands what the hell we're doing," says CIA Director Leon Panetta.

According to Brennan, the U.S has succeeded in weakening al-Qaeda’s ability to recruit and train.

"And so what comes out of that pipeline, I think, is a much less capable, much less expert terrorist. If their underwear doesn't explode the way it's supposed to, it's not just because the guy was incompetent. It's because the training he got, the person who provided him the IED, the materials that went into it — all were less efficient, less suitable to the challenge,” he said.

His continued focus remains on protecting the U.S. from terrorist attacks. He told “Frontline” he views the war on terror not as a battle, but a a global campaign to stamp out terrorism.

He has come along way from his humble beginnings to the pinnacle at the White House, but Brennan has paid tribute to the parents who nurtured hm and helped him succeed.

In that respect, he is not unlike another son of Roscommon emigrants, former Supreme Court Justice William Brennan, who was also from New Jersey.

It seems when it comes to achievement and accomplishment, the sons of Roscommon have something special.