* Rothschild's RIT Capital buys Rockefeller stake from SocGen
* Deal gives Rothschild long-sought foothold in United States
* Rockefeller CEO sees broad benefits from the combination
LONDON, May 30 (Reuters) - Two of the most storied names in global finance are linking up, with Europe's Rothschild banking dynasty agreeing to buy a stake in the Rockefeller group's wealth and asset management business to gain a long-sought foothold in the United States.
Rothschild's London-listed RIT Capital Partners said on Wednesday it was buying a 37 percent stake in Rockefeller from French group Societe Generale's private banking arm, for an undisclosed sum.
The transatlantic union brings together David Rockefeller, 96, and Jacob Rothschild, 76 - two family patriarchs whose personal relationship spans five decades.
"We are combining, on a macro level, two well-recognized names and families who have a long history of wealth creation and responsible stewardship," Rockefeller Chief Executive Reuben Jeffery said in an interview.
Specific business initiatives arising from the new partnership have not yet been determined, Jeffery said. "It will take us time to work out the details."
One area where Rockefeller's clients may benefit, he said, is access to Rothschild's direct private equity investments.
Rockefeller & Co traces its origins back to 1882 when it was founded as one of the world's first family offices by Standard Oil baron John D. Rockefeller to manage his personal wealth. It became a U.S.-registered investment adviser in 1980 and has since developed into a wealth and investment manager overseeing $34 billion for ultra-rich families, trusts, endowments and other institutions.
Banks across the world are shedding noncore assets to reduce risks and strengthen capital positions to meet tough regulations aimed at preventing a repeat of the 2008 financial crisis.
Reuters earlier this month reported that SocGen was in early talks to sell a Los Angeles-based asset management unit, Trust Co of the West, to its management, among other options. The French bank also has been selling billions of euros' worth of aircraft, shipping and real estate loans to shrink its balance sheet and reduce U.S. dollar funding needs.
SocGen, which has held its stake in Rockefeller since 2008, appointed a new head of private banking in March, replacing Daniel Truchi with Jean-Francois Mazaud as it moved to overhaul the business.
But for Rockefeller, the latest deal replaces SocGen with one of the best-known names in global finance.
The Rothschild banking dynasty began when Mayer Amschel Rothschild started a business in Frankfurt in the late 18th century. The family has worked on some epochal deals during its history, such as helping finance Britain's war against Napoleon in the 19th century and raising funds for a loan allowing the British government to buy the Suez canal.
RIT and another of the family's companies, Edmond de Rothschild Group, said earlier this year they would form a new joint venture to boost their fund management and investment operations.
The deal is expected to close by the end of September, pending regulatory approvals.