Roughly 30 members of the sixth generation, aged between 15 and 30, are contenders to see if they could one day run Wallenberg's Investor holding company and several foundations with major stakes in Electrolux, Atlas Copco and Ericsson.
There are no clear favorites and the job could also go to an outsider, but whoever is picked to lead an empire so famous a popular beef dish takes the family name, will have to decide if it should invest in new and faster growth companies beyond its financial and industrial roots.
In egalitarian Sweden, the family is seen as a model of how to expand a company through generations without squabbles and the appointment will be made according to experience rather than assertions of birthright.
Wallenberg, who has not indicated he plans to step down, organizes seminars for some young family members at an old estate.
"They have to get the experience, and then we’ll see what happens. And the sixth generation is in the middle of that right now," said Jacob Wallenberg, sitting in his wood-paneled office five minutes walk from Stockholm's Royal Palace.
The empire began in 1856 when Andre Oscar Wallenberg founded Stockholms Enskilda Bank, now part of SEB. The family's fame and influence grew with the company, helped by the construction of a wealthy Stockholm suburb and one scion who became a hero for saving Jews in Hungary in World War II.
While many family empires implode in feuds or have the assets split by an ever growing number of descendents, the Wallenbergs have so far avoided this.
They began channeling their wealth into non-profit foundations in 1917, which control over 50 percent of voting rights in Investor and other assets in an empire that is today largely run by Jacob and his cousin Marcus.
"The Wallenbergs separated the money from the power," said Gunnar Wetterberg, author of "Wallenberg - A family empire".
"The harmony that appears to exist today between the cousins is not at all a foregone conclusion."
The Wallenbergs are wealthy but not among the top 100 richest Swedes listed by magazine Veckans Affarer. Jacob Wallenberg earned some $320,000 last year in salaries from his chairmanship of Investor, according to the firm's annual report.
"It sort of boils down to that we are not personally owners of this. We cannot run into the squabble part," Wallenberg said. "I have to go to a job and earn my living, like everyone else."
He gradually took over from his grandfather. He had worked at SEB after spending several years in the navy and getting an MBA in the United States.
History has made the family wary of the pressures of the job. Jacob's uncle, Marc Wallenberg, slated to assume the helm of the empire, committed suicide in 1971, shocking Sweden.
His daughter, Caroline Ankarcrona, made headlines when she became the first female family member to sit on the board of the Knut and Alice Wallenberg Foundation and Jacob Wallenberg said he would like to see more women coming through.
Under Jacob and Marcus Wallenberg as well as CEO Borje Ekholm - a family outsider - Investor has moved into unlisted companies from medical services to schools. Unlisted firms have jumped to nearly a quarter of Investor's holdings.
Still with most holdings in a comfort zone of listed blue chips, some investors would like a more aggressive strategy. It is something the Wallenberg's largely fend off, with a priority on long term planning rather than quarterly deadlines.
Others say Investor has moved too slowly. It entered healthcare and champions R&D spending, but it shunned high growth consumer technology, in contrast to family-run Kinnevik.
"I think he (Jacob) is a bit risk averse," said an executive who has worked with Wallenberg for more than a decade.
Some point to rival Swedish holding company Kinnevik and its bold bets on fast-growing online ventures such as Zalando, but for all that Investor shares are up 129 percent over the past three years versus an 82 percent gain in Kinnevik.
"Over time I wouldn't be surprised if you saw one or two more unlisted companies," said Wallenberg. "But is it something where you see quick moves, significant moves? No. "We're working on buying to hold rather than buying to sell."
Business relationships fostered over more than a century often give even existing holdings an edge when deals are struck in sectors familiar to the Wallenbergs, such as in Electrolux' $3.3 billion buy of General Electric's appliances business.
"I think when it comes to the long-term relationship between GE and Electrolux, it went through the Wallenbergs," said Electrolux chairman Ronnie Leten.
"When it comes to the CEOs of these big international companies, the Wallenbergs know these people."
(Additional reporting by Johannes Hellstrom and Mia Shanley; Editing by Anna Willard)
By Alistair Scrutton and Niklas Pollard