Связать базу данных (потомок, родители) с глобальной переменной

(setf family ’((colin nil nil) (deirdre nil nil) (arthur nil nil) (kate nil nil) (frank
nil nil) (linda nil nil) (suzanne colin deirdre) (bruce arthur kate) (charles
arthur kate) (david arthur kate) (ellen arthur kate) (george frank linda) (hillary
frank linda) (andre nil nil) (tamara bruce suzanne) (vincent bruce suzanne)
(wanda nil nil) (ivan george ellen) (julie george ellen) (marie george ellen)
(nigel andre hillary) (frederick nil tamara) (zelda vincent wanda) (joshua ivan
wanda) (quentin nil nil) (robert quentin julie) (olivia nigel marie) (peter nigel
marie) (erica nil nil) (yvette robert zelda) (diane peter erica)))

(defun parents (person family)
  (cond ((null family) nil)
        ((eq person (caar family)) (if (equal '(nil nil) (cdar family)) nil (cdar family))) 
        (t (parents person (cdr family)))))
 
==> parents
 
(defun grand-parents (person family)
  (let ((par (parents person family)))
       (append (parents (car par) family) (parents (cadr par) family))))
  
==> grand-parents
 
(grand-parents 'joshua family)
 
==> (george ellen)
 
(grand-parents 'julie family)
 
==> (frank linda arthur kate)