(FORTUNE Magazine) – Almost from the time he was tall enough to reach a TV dial, Brian Roberts was intrigued by his old man's cable business. As a boy he punched the coupon books mailed to Comcast's customers. As a teenager he tagged along to meetings with Comcast's bankers. After he graduated with a degree in finance from the Wharton School, his dad urged him to earn a living elsewhere. But the son wanted to work only for his father, who finally relented--on condition that Brian start humble. "Go climb the poles," said Ralph Roberts.

Two decades later Brian Roberts is the man who would be cable's king. In July, Comcast launched a $52 billion bid for AT&T Broadband. AT&T has since cast about desperately for alternatives--among them, taking its broadband unit public. But nothing had materialized through September, when AT&T finally signed a confidentiality agreement with Comcast that will let the due diligence--and perhaps even real negotiations--begin in earnest. If Comcast succeeds, it would become the nation's No. 1 cable operator, with 22 million subscribers (passing AOL Time Warner, parent of FORTUNE's publisher), and Brian Roberts would exert huge power over cable's programmers--and its destiny in a broadband world.

Comcast also would become even more of an anomaly than it already is. Most of Ralph Roberts' contemporaries--early mom-and-pop cable operators--cashed out over the past 15 years as the business became increasingly complicated and competitive. Comcast has grown eightfold in that time while remaining a staunch family company; although it has been public since 1972, the Robertses own 87% of the voting stock. And while Comcast's bid for AT&T Broadband seems to be just another game of corporate hardball, it has an unusual soft core: a father-son love story.

The setting for the story is the City of Brotherly Love, where from Comcast's 35th-floor headquarters you can all but shake hands with the statue of William Penn atop Philadelphia's city hall. Ralph and Brian Roberts have adjoining offices, separated by a glass door through which they traverse and converse many times a day. At age 81, when he could be in his dotage, Roberts pere is in his office four days a week and remains chairman. At age 42, when he could be asserting his independence, Roberts fils is president and embraces his dependence on Dad. Confronted with the biggest decision of his career this summer, Brian waited until Ralph returned from a European vacation so they could have a heart-to-heart before launching Comcast's unsolicited bid for AT&T Broadband.

"Ralph and Brian have the most remarkable father-son relationship I've seen in any context," says Leo Hindery, former president of AT&T Broadband. "Rather than battling each other, as fathers and sons often do in a family business, they have this supportive, loving relationship."

That gives Comcast a kinder, gentler face in an industry of buccaneers. But the Robertses reserve their warmth for the office. Out on cable's open seas, they are stone cold killers. Brian is the more nakedly driven--aspiring to be an industry alpha and reputed to be perhaps its toughest negotiator. Ralph's ambition burns no less strong but is masked by soft voice and bow-tied dress. In reality, it is he who steels Brian to make bold moves, his strong gut instincts validating his son's intellectual analysis. The synthesis of the two has created a formidable company.

Ralph Roberts started humble in 1963, with a 1,200-subscriber cable television franchise in Tupelo, Miss. He'd already been in such varied businesses as golf, cologne, Muzak, and suspenders, so he knew he was onto something with this one when, he says, "People chased our truck down the street, yelling, 'Please stop at my house!' " Comcast began its growth spurt in the mid-1980s by making a $2.5 billion bid for Storer Communications, which owned television stations and cable franchises. Although leveraged-buyout leviathans Kohlberg Kravis Roberts wound up winning Storer, Comcast's bid served public notice that the company had arrived. Afterward, chief financial officer Julian Brodsky told Ralph Roberts that if he took Comcast private, he could get rich. "I don't want to be rich," Roberts replied. "I want to build a great public company that I can turn over to Brian."

In 1985, Comcast joined a consortium of operators that bought and divvied up Westinghouse's cable systems. Comcast's slice added 600,000 subscribers and doubled its size. In partnership with TCI's John Malone, Ralph then bought Storer's cable systems from KKR, making his company the fifth-biggest cable operator. When Turner Broadcasting System was swamped with debt, Comcast joined a cable-industry bailout. Though Comcast's portion of the capital infusion was just $5 million, it got a spot on the Turner board. Ralph Roberts could have sat with industry lions like Malone and Time Warner's Gerald Levin. Instead he sent 29-year-old Brian. "It was an important experience for Brian," says Terry McGuirk, a Turner executive and Roberts friend. "The people who sat around that table were the most powerful in the industry, and Brian was recognized as a peer."

In 1990, Ralph kicked himself upstairs to chairman and named Brian president. "Ralph set the tone that this company was either going to grow or die, but he could be happy with a 50,000-subscriber deal," says Brodsky. "Brian always thinks of hitting the ball out of the park." That's how Brian came to recruit Barry Diller to operate shopping channel QVC, whose biggest shareholder was Comcast. It was an odd match, given that Diller runs with the glitterati and the Robertses live private family lives. But Brian thought Comcast was short on content to sell to other cable operators, and Diller, who had just left the Fox Network, was long on talent.

Both saw QVC as a splendid acquisition vehicle--but they didn't always agree on the targets, which doomed the partnership. The Robertses did back Diller's unsuccessful bid to buy Paramount, but balked in 1994 when he tried to merge QVC and CBS in a deal that would have made Diller the network's CEO. Soon after CBS began its tender offer, Brian and Ralph met Diller at Teterboro (N.J.) Airport. Ralph gave Diller a letter saying that Comcast was ready to make a higher offer for the 85% of QVC it didn't already own. This may as well have been a stiletto between the ribs. CBS folded, and Comcast, again in partnership with TCI, bought QVC for $2.2 billion. "I saw the difference between the bow-tied Philadelphia gentleman and the tough-as-steel businessman," says Diller of Ralph.

To Ralph, whose wealthy parents lost their fortune during the Depression, that's the way of the world: Seize opportunities or get seized. The AT&T deal is just the latest, biggest manifestation of that mindset. "Being raised in the Depression and the Holocaust gave my father a somewhat paranoid mentality," explains Brian, who says the quality may be even more pronounced in him.

Certainly Brian has had stretches as Comcast's president where there was reason to be paranoid: Congress re-regulating the industry and capping rate hikes; Congress inviting the Baby Bells to compete in cable; satellite competitor DirectTV threatening to capture millions of cable's customers. For a time he and his father wondered whether they should stay in cable at all, and they concentrated their major investments in a cell-phone subsidiary. "We did some soul-searching," recalls Brian. "Was the cable industry obsolete? Was it an opportune time to get out? Our conclusion was that if you rebuilt your system with this new fiber-optic coaxial hybrid--which we now call broadband--the glass was half full, not half empty. We could compete." So the Robertses took their cable systems digital and turned them into tomorrowland: 200 channels, high-speed Internet access, video on demand, the works. It cost $5 billion and severely tested the company. "We had to borrow every cent when we began the rebuild in 1995," says treasurer John Alchin.

Comcast returned to prosperity in 1997, courtesy of Bill Gates. A group of cable moguls was dining with him in Seattle, when Gates began to question them about broadband: How could its terribly slow buildout be accelerated? "Why don't you buy 10% of the industry?" asked Brian Roberts. "Most of us are here tonight." Some of his peers were aghast at his audacity, and Roberts even told his father that he might have overdone it. But he returned to Philadelphia to discover that Gates wanted to buy 10% of one company: his. Besides the capital infusion that drove the wolves from the door, Microsoft's investment gave Comcast a Good Housekeeping seal of approval. "We were getting asked by investors, 'What's the payback on this rebuild? When is it coming?' " says Brian. "I never got that question again."

It's nearly finished now, the culmination of a great run for Comcast. The company has doubled its subscriber base in four years. Its 45% operating margins are among the cable industry's fattest, partly owing to the increased fees it reaps for added services. It's made moves to strengthen its content by buying the Philadelphia Flyers (hockey) and 76ers (basketball) and building a regional sports network around them. Even its setbacks have turned out well. When it failed to acquire MediaOne, with which it had a tentative deal in 1999, it got a $1.5 billion breakup fee from victor AT&T Broadband, plus two million AT&T subscribers.

That's a consolation prize compared with the big trophy: 14 million subscribers from AT&T Broadband. Comcast still hasn't clinched it, as AT&T continues talks with others, including Microsoft, which could ally itself with whoever best served its broadband interests. But the Robertses want this deal bad: In cable, size matters. With 22 million subscribers, Comcast would have the power to make or break programmers, who desperately need mass distribution. It also could do more to shape cable's technologies, priorities, and content. "If [the post-acquisition] Comcast and AOL Time Warner wanted a new music channel to compete with MTV, they'd have 33 million homes on day one," says Tom Wolzien, a Sanford C. Bernstein analyst.

But the deal would also be risky, for as Wolzien puts it, "This is a monster to assimilate." AT&T Broadband--nearly twice as big as Comcast--is still trying to digest its own megasystems; its margins are less than half of Comcasts'. The Robertses do have plenty of experience managing great leaps forward. Their crack operations people parachute into acquired systems and make them run the Comcast way. But AT&T Broadband is so much bigger than anything else Comcast has bought that the task dwarfs what has gone before.

That leaves two central questions for Comcast: How does the company maintain its agility and avoid becoming unwieldy? And how does it attain scale yet maintain its tradition of family control? To make this a tax-free deal, Comcast must issue AT&T shareholders 51% of the combined company, which effectively cuts the Robertses' present 87% of voting stock in half. "At a certain point, control and size are mutually exclusive," says Diller, now CEO of USA Networks, a cable programmer. He thinks that if Comcast buys AT&T Broadband, "it's probably at that crack point."

On the other hand, as Diller himself discovered, the Robertses aren't to be underestimated. Nor can their competitive streak be overestimated. Years ago, as a boy, Brian sometimes rounded out a tennis foursome that included his dad and two co-founders of Comcast. When Brian was 8, the other team used to trounce him and Brodsky, his regular partner. By the time Brian was 12, Brodsky chortles, "He and I killed them." Brian switched rackets at Penn, where he went from being one of the worst players on the squash team as a freshman to an all-American as a senior. He still plays a strong game, according to frequent partner David Proctor, one built on a keen sense of strategy, a knack for playing the angles, and a fierce will to win. Recognize those qualities, cable guys? Be on the lookout for more bold strokes from Comcast.

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