Citigroup's private banking arm has set up a global unit to target family offices, organizations that manage the financial affairs of rich dynasties, according to an internal memo seen by Reuters.

Citi has promoted Catherine Weir, chief executive for the Europe, Middle East and Africa (EMEA) region to lead the new global family office group, reporting to Jane Fraser, global head of Citi Private Bank.

Replacing Weir as CEO of the EMEA business is Luigi Pigorini, global head of investment finance for the private bank, the memo said.

Family offices are mini financial institutions that manage the riches of single families, though many have started to diversify into taking on multiple clients.

The U.S. bank's push to formalize its offer of products and services to family offices around the world follows a strategic realignment of the private bank to target super-rich clients worth more than $25 million, over the merely affluent.

Citi sold a controlling stake in its Smith Barney retail brokerage to Morgan Stanley, moving away from a U.S-style wealth management model.

Following the reorganization, Citi Private Bank is estimated to have between $100 billion to $150 billion in assets under management - putting it in the global top 25 wealth managers.

The private bank's global head told Reuters in an interview earlier this year she was seeking to internationalize the client base away from a U.S. focus and increase its share of group revenue.

Both Weir and Pigorini will be based in London.

(Reporting by Chris Vellacott; Editing by Erica Billingham)