The Walton family. Walmart, Samsung, Koch Industries and Hermes have built some of the biggest fortunes to ever be handed down between generations. Bloomberg

The saying, or at least the sentiment, sounds familiar in any language: “Shirtsleeves to shirtsleeves in three generations.”

The adage is often attributed to Andrew Carnegie, but the notion that family wealth ends up squandered travels far. “Stable to stars to stable,” an Italian version goes. “From paddy to paddy in three generations,” runs the Chinese saying.

But in an era of mind-boggling wealth and gaping inequality there seems little danger of that happening any time soon to the world’s 25 richest clans, who control $1.1 trillion of wealth, according to data compiled by the Bloomberg Billionaires Index.

From Mars bars to Hermes scarves, supermarkets to hotels and data firms to drug makers, the source of this wealth is varied and its scale is startling: more than the market cap of Apple, all the deposits held by Citigroup or the entire GDP of Indonesia.

And any calculation is likely to be a lowball figure. The wealth of families like the Rothschilds or Rockefellers is too diffuse to value. The nature of many dynastic fortunes — backed by decades and sometimes centuries of assets and dividends — can obfuscate the true extent of their holdings. Clans whose source of wealth is currently unverifiable or derives primarily from the state, such as the sprawling House of Saud, are also absent.

Bloomberg’s categorization of family wealth also excludes first-generation fortunes and those in the hands of a single heir. That means just three Asian families make the list and none from China, reflecting the relatively recent wealth boom experienced by the region. That should soon change. Family offices are proliferating in the region and tycoons like Li Ka-shing are starting to hand over their empires to their sons and daughters.

The dwindling of once-storied fortunes like the Pulitzers, Vanderbilts and Woolworths illustrate how common it is for even the biggest family fortunes to be squandered. “There are a host of hurdles families must tackle to ensure that their wealth is safeguarded through the generations,” said Rebecca Gooch of Campden Wealth. “Strategic planning, education and communication is key.”

Some billionaires are taking a different tack. Bill Gates and Mark Zuckerberg are among the entrepreneurs who have signed up for Warren Buffett’s Giving Pledge and committed to dedicating the majority of their wealth to philanthropy.

This approach embodies another Carnegie dictum: “To spend the first third of one’s life getting all the education one can. To spend the next third making all the money one can. To spend the last third giving it all away to worthwhile causes.”