Seymour Pierce, the city brokerage run by football financier Keith Harris, could try to claim up to £7m from the Al Khorafi family, should the Kuwaiti group succeed in buying Liverpool Football Club.
The brokerage has filed a writ against the family at the London High Court, alleging that Rafed Khorafi failed to pay Mr Harris introduction fees to meet Liverpool's owners, Tom Hicks and George Gillett.
Filed on 25 February, the writ demands more than £300,000 in unpaid advisory fees. Advised by City lawyers Rosenblatt, Seymour Pierce could demand up to £7m in a success fee from Mr Khorafi, should he take over the Premiership football club.
The writ claims that Mr Khorafi has already admitted "liability of the initial fee" of £100,000 and additional disbursements worth £19,000.
An adviser to Mr Khorafi was unavailable for comment.