RIT Capital Partners is to buy a 37 per cent stake in the Rockefeller’s wealth advisory and asset management group for an undisclosed sum, giving Lord Rothschild’s London-listed trust a much sought-after foothold in the US.

The transatlantic union brings together David Rockefeller, 96, and Lord Rothschild, 76—two family patriarchs whose personal relationship spans five decades.

The Rockefeller group traces its roots back to 1882 when John D. Rockefellerestablished one of the world’s first family offices dedicated to investing his wealth. It has since developed into a provider of wealth and asset management services to other families, foundations and institutions. It is majority-owned by the 19th century oil magnate’s family and has $34 billion of assets under management.

The partnership with RIT will focus on setting up investment funds, eyeing joint acquisitions of wealth and asset managers and granting each other non-executive directorships.

RIT Capital Partners is minority-owned by Lord Rothschild and its net assets of £1.9 billion ($2.97 billion) are spread across global investments from public equities to government bonds and private equity.

The deal stemmed from a meeting two years ago when Mr Rockefeller introduced Lord Rothschild to the US group’s chief executive, Reuben Jeffery.

In a follow-up meeting one year later at Lord Rothschild’s office at Spencer House in London, the financier won Mr Jeffery’s blessing for opening talks to buy a stake in the Rockefeller group.

He then launched long negotiations with Société Générale Private Banking, which has owned the shareholding since 2008.

The French bank’s wealth management arm has had several suitors for the minority stake – estimated to be worth less than £100 million ($156.2 million) – but Lord Rothschild was the only one supported by the Rockefellers.

Sir Evelyn at the time ran NM Rothschild, which rose to fame in 1815 when Nathan Meyer Rothschild made a fortune buying British government bonds in anticipation of Napoleon’s defeat at Waterloo.

Baron David de Rothschild, chairman of the Rothschild Group, is currently bringing the UK-based investment bank under a joint roof with the French family operations.

At the same time Lord Rothschild launched an investment partnership this March with the Franco-Swiss private bank Edmond de Rothschild Group, which is yet another separate branch of the sprawling banking dynasty.