(setf pair-lst '((a  b)
                 (b  c)
                 (c  d)
                 (c  e)
                 (a  f)
                 (d  x)
                 (y  z)
                 (z  c) ))

(defun gen-family-relation (list env)
  (let ( node result )
	(dolist (x list result)
	    (setf node (assoc (car x) env))
		(if node
		    (setf (cdr node) (append (cdr node) (cdr x)))
		    (push x env) )
		(setf result env) )))

(defun query (s env)
  (let ((node (assoc s env)))
    (if node
        (cons (car node)(mapcar #'(lambda (x)(query x env)) (cdr node)))
        s)))