The Wales defender, who started Saturday's 3-1 win over Crystal Palace, has told the club that his pregnant wife now refuses to stay in the north and that he wants to return to London.
Kevin Keegan has agreed to let him go, but not until he has found a replacement, while Fulham have agreed to pay £500,000 for the left-back, marking a significant profit on the £100,000 City paid Leicester for the 29-year-old last summer.
“I have a deal with Ben to go to Fulham for family reasons,” KK told the M.E.N. “Ben came to me a week ago absolutely mortified as to what had happened to him.
“He has been robbed twice. It was a very scary thing. His wife would not come back. We love him to bits at this football club but some things are more important."
“Some people might say I am a softy but I don’t want Ben here while his family and kids are down south," added the City boss.
“We have done the deal but he has to have a medical and wait for me to get a replacement. He has made a big impression around the football club. He is a very obliging lad and we will miss him.”