(let ((mom-path (cons 'dad '()))
      (dad-path
        (if (eq? 'brown '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)))