(let ((mom-path (cons 'dad '()))
      (dad-path
        (cond
         ((eq? (make-ft 'bill 'brown 'unknown 'unknown) 'unknown) #f)
         (else
          (if (eq?
               (ft-eye-color (make-ft 'bill 'brown 'unknown 'unknown))
               'blue)
            '()
            (let ((mom-path
                    (path-to-blue-eyes
                      (ft-mom (make-ft 'bill 'brown 'unknown 'unknown))))
                  (dad-path
                    (path-to-blue-eyes
                      (ft-dad (make-ft 'bill 'brown 'unknown 'unknown)))))
              (cond
               ((and mom-path dad-path) (cons 'mom mom-path))
               ((and mom-path (not dad-path)) (cons 'mom mom-path))
               ((and dad-path (not mom-path)) (cons 'dad dad-path))
               (else #f))))))))
  (cond
   ((and mom-path dad-path) (cons 'mom mom-path))
   ((and mom-path (not dad-path)) (cons 'mom mom-path))
   ((and dad-path (not mom-path)) (cons 'dad dad-path))
   (else #f)))