Brady and Sullivan have been involved with Birmingham since 1993
Chief executive Karren Brady and plc chairman David Sullivan will leave Birmingham if Carson Yeung takes over the Premier League club.
Hong Kong businessman Yeung lodged his buyout bid for Blues on Tuesday after sending official offer documents to shareholders offering £1-per-share.
Sullivan and Brady will end their 16-year association with Birmingham providing the deal goes through.
But Sullivan, Blues co-owner, said he "intends to remain in football".
Yeung's company, Grandtop International Holdings, already owns 29.9% of the club, and co-owners Sullivan and the Gold brothers have indicated they will sell their combined 50% investment, although David Gold is set to stay on as chairman.
If Yeung's stake reaches 90%, it will trigger the compulsory purchase of the remaining shares.
The first closing date of the offer is 6 October, after which time Grandtop International Holdings will assess its level of ownership.
Sullivan, 60, founded the Sport newspaper group in 1989, publishing the Daily Sport and Sunday Sport, before selling his stake for £40m in 2007.
After taking charge of Birmingham when it was in financial administration in 1993, Brady and Sullivan have turned the club's fortunes around.
As the duo prepare to move on Sullivan has indicated he would like to invest in another football club, while Brady hinted the pair may continue their partnership in the future.
"Following the takeover I will be looking for a new challenge where my experience, my success and sound business acumen will make a difference," said Sullivan, who has been reportedly interested in investing in a London-based club.
Meanwhile, Brady is to take over from Margaret Mountford as an adviser to Lord Alan Sugar on the television show The Apprentice.
I would like to thank all the fantastic supporters for welcoming a 23-year-old woman into the club, and sticking with me into middle age!
The 40-year-old became the youngest managing director of a plc when the club was floated on the stock market in 1997 and has been referred to as the first lady of football, as she is the highest placed woman in the game.
"I leave with very fond memories of the past 16 years - I arrived with David Sullivan in 1993 and I want to leave with him. Whatever he does in the future, you can rest assured I'll be standing by his side," she said.
"I would like to thank all the fantastic supporters for welcoming a 23-year-old woman into the club, and sticking with me into middle age!
"Grandtop have asked me to retain my position as CEO but I honestly feel they must be allowed to stamp their own mark on the club and I believe that this is best done without the current board looking over their shoulder."
Yeung, who launched a failed bid to buy the Blues in 2007, has already secured a £57m bridging loan to finance the deal.
He is now seeking permission from backers to issue 50% more shares in Grandtop at an extraordinary general meeting scheduled for next month. However, the acquisition of Birmingham is not dependent on that being successful.
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