The former professional footballer was appearing on BBC Radio 4's Desert Island Discs to celebrate the show's 75th anniversary.
"People have talked about 'do we stay together because it's a brand?' Of course not," he said.
"We stay together because we love each other. We stay together because we have four amazing children."
He told presenter Kirsty Young: "We're a strong family unit. We've got strong parents, we were brought up with the right values.