Lord Rothschild's London investment trust has teamed up with his French cousin's private bank to form a joint asset management business.
Jacob Rothschild's RIT Capital Partners will hold 49 per cent of the joint venture and Edmond de Rothschild Group, which is headed by Baron Benjamin de Rothschild, will have 51 per cent. Edmond de Rothschild Group is injecting its existing fund management company, which handles $2.7bn (£1.7 bn), in return for £14m worth of new shares in RIT.
Baroness Ariane de Rothschild, Benjamin's wife, becomes honorary vice chairman of RIT and Lord Rothschild takes a similar role at the French holding company.
The joint venture will give RIT Capital greater access to European markets and deal flows.
Lord Rothschild said, "We are excited by the prospect of closer co-operation."