Under Brian Roberts, Comcast has built on its standing as a cable television power to become a media and entertainment giant in content creation and Internet and voice services.

In 2011, fulfilling the Robertses’ long-held interest in NBC, Comcast acquired a majority stake in NBCUniversal from General Electric for $6.5 billion; in doing so, it became one of the industry’s leading content producers.

Image Mr. Roberts bought a small cable service in Tupelo, Miss., and built it into Comcast. Credit... Manuel Balce Ceneta/Associated Press

Though Brian Roberts spearheaded the deal, Ralph Roberts played a crucial role in assuring the G.E. chief executive, Jeffrey R. Immelt, that the deal would be completed. At one point, Ralph Roberts met with Mr. Immelt without Brian Roberts. Mr. Immelt “was aware that many deals don’t get concluded,” the elder Mr. Roberts was quoted as saying in “The Incredible Dream,” a 2012 biography by William Novak, “and he wanted some reassurance from the father of the groom that we wouldn’t let this opportunity slip through our fingers.”

In February 2013, Comcast paid $16.7 billion to purchase the remaining stake in NBCUniversal.

In 2014, Comcast proposed a $45.2 billion acquisition of Time Warner Cable. The deal stirred up widespread opposition from factions who feared that the resulting cable industry giant would stifle competition and hurt consumers. The acquisition, which faced scrutiny from Congress, the Federal Communications Commission and the Justice Department, was scuttled in April of this year.

Mr. Roberts, typically dapper in his signature bow tie and Brooks Brothers suits, became his son’s mentor and sounding board, and the two were admired as a potent business partnership while never displaying the kind of strained and tempestuous relationship that can flare when a son succeeds a successful father.

“Since I was 12, all I wanted to do was work with my dad,” Brian Roberts said in an interview for this obituary. “I believe the reason we are still in this business when so many others have long since departed was his will to succeed, and to do it with certain core values and integrity. Maybe it was losing both his parents before he was 21, living through the Depression, but somehow he became an optimist. He was the most optimistic man I ever knew. He never told me anything I wanted to do at Comcast was a bad idea, and after more than 30 years, you’d think I’ve had a lot of bad ideas.”