Generations of Boston residents have watched that story play out in the real-life drama of former Democratic Senate President William "Billy" Bulger and his older brother, alleged gangster James "Whitey" Bulger.

At the heart of the story, at least for the younger Bulger, was a fierce loyalty to family and the shared experience of growing up in the working class Irish-American enclave of South Boston, where the line between brawling and bare-knuckled politics was easily blurred.

The two brothers also shared one more thing: a willingness to use whatever power was available to them.

In William’s case, that was a savviness for street-smart politics that propelled him into one of the most powerful positions in Massachusetts state government, where he earned a reputation for arm-twisting that rarely saw him lose a battle.

For Whitey, according to an inch-thick pile of indictments, that power came at the barrel of a gun and a coterie of enforcers.

Whitey’s surprising arrest after 16 years on the run to face 19 murder charges this week has again thrust the brothers’ story into the spotlight.

It’s a relationship that would dog William Bulger throughout his career, ultimately forcing his resignation as president of the University of Massachusetts system in 2003 after he testified before a congressional committee investigating the FBI’s ties to his brother, who by then had been revealed as an FBI informant.

After receiving immunity, William acknowledged receiving a call from Whitey shortly after he fled.

"The tone of it was ‘Don’t believe everything that is being said about me,’" William Bulger said. "I think he asked me to tell everybody he was OK. … I think I said I hope this has a happy ending."

Two years earlier, William Bulger had told a grand jury he didn’t urge his brother to surrender because he didn’t "think it would be in his interest to do so," according to a transcript of his testimony obtained by The Boston Globe.

"It’s my hope that I’m never helpful to anyone against him," the younger Bulger said, according to the transcript. "I don’t feel an obligation to help everyone to catch him."

Among those pressing William Bulger to resign from his university post was then-Republican Gov. Mitt Romney.

For William Bulger it was a role as defender of his brother that he’d long ago accepted, even as Whitey allegedly disappeared into an increasingly violent criminal netherworld.

In his 1996 memoir "While the Music Lasts," William Bulger described Whitey, five years his senior, as being in "a constant state of revolt," and as "restless as a claustrophobic in a dark closet."

Whitey kept himself in top physical shape, neither smoke nor drank, shunned addictive drugs, and had "an abundance of good humor and a wildly creative talent for impish mischief," his brother wrote.

But William Bulger also said Whitey found himself in trouble with police and once ran away to join the circus — signing on with Ringling Brothers and Barnum & Bailey Circus as a roustabout. The older brother joined the Air Force but had trouble conforming and was later discharged.

"He was just being Jim," Bulger wrote.

William Bulger said that it was around this time that Whitey fell in with a crowd involved in bank holdups and in 1956 was convicted of involvement in three bank robberies and sentenced to 20 years. He served part of what turned out to be an 11-year sentence in Alcatraz.

Four years after Whitey’s conviction, William was first elected to the Massachusetts House.

In the years following Whitey’s release, William blamed the press for spreading what he called "lurid allegations" about his brother, speculating that some of the "dark rumors" were nothing more than political attacks on him.

As Whitey’s criminal activities allegedly turned more brutal, William Bulger rose through the Statehouse ranks. In 1970 he won a Senate seat and eight years later was elected Senate president by the 40-member chamber, a position he would hold for a record 17 years.

Even after Whitey fled in 1995 of the eve of his indictment on racketeering charges, William remained loyal, accusing overzealous prosecutors of buying testimony with promises of early release from prison.

"It has been known for many years that a ‘get out of jail’ card has been available to anyone who would give testimony against my brother," he wrote.

At the same time, William was earning a reputation as a tough-minded leader who rewarded supporters and punished critics.

Warren Tolman, a former Democratic senator who was among those critics, served briefly under him.

Tolman said that although he often found himself at loggerheads with William Bulger, he felt Bulger treated him fairly and could be "a charming guy" when he wanted.

Still, Bulger wasn’t shy about using his political might.

Tolman said after he was able to prevent a transportation funding proposal from passing by a single vote, Bulger, who opposed the measure, used his muscle to flip a vote, forcing the proposal through.

"By and large he got his way whenever he wanted," Tolman said. "You knew that if you took him on it was going to be an uphill battle."

Tolman said he never recalled open discussions about Bulger’s brother even his Senate colleagues "certainly knew of the legend of Whitey Bulger."

"I don’t think anyone ever realized the scope of the dastardly deeds he’s accused of," Tolman said.

Occasionally the lines between politics and the underworld blurred.

In 1994, then-state Sen. William Keating led a group of like-minded liberal lawmakers in an attempt to oust Bulger as Senate president.

Although the challenge failed, the campaign against Keating was fierce. Keating said his supporters from South Boston told him that Whitey had paid people to travel to Keating’s district to hold signs for his Republican opponent.

Keating said he had his own brief run-in with the reputed mobster, who approached him and lit into him with a barrage of profanity-laced insults for trying to take down his brother.

Keating, who went on to become Norfolk District Attorney before being elected to Congress last year, said he’s friends with a family who lost a loved one to Whitey’s violence, according to the indictments against him.

"There’s a tendency to glamorize abuse of power and a tendency to glamorize the gangster life, but as a district attorney I was there as they were unearthing the bodies of (Whitey Bulger’s) victims," Keating said. "It’s not funny and it’s not glamorous. It was savage and it was brutal."

In a written statement following Whitey’s arrest this week, William Bulger said he wished to "express my sympathy to all the families hurt by the calamitous circumstances of this case."

Then, during Whitey’s brief appearance in federal court in Boston on Friday, the aging brothers had a fleeting reunion of sorts. Whitey, now 81, smiled at his younger brother and mouthed the word ‘Hi.’ William smiled back.

William, speaking briefly to reporters as he left the courthouse, appeared emotional.

"It’s an unusual experience," he said.