Both men have children diagnosed with a rare disease called Fanconi anemia, which leads to bone marrow failure.
London donated bone marrow to his daughter, Ticynn, when she was diagnosed as a child. She is now a healthy 16-year-old.
Fisher's son Ethan was diagnosed within the last year.
"We talked as not two football coaches but as two fathers," London said. "Two fathers whose children, one who had gone through and one who is about to go through."
Florida State is holding a bone marrow registry drive on Saturday. And the two men have joined together for a public service announcement that will run during the game.
"We did Ticynn's bone marrow transplant at Johns Hopkins Hospital," London said. "I believe the success rate was in the high-60, 70 percent. And talking with Coach Fisher now I believe it's in the high-80, 80 percentile."