(defclass foo ()
  ((name :initarg :name :accessor name :initform nil)
   (value :initarg :value :accessor value :initform nil)
   ;; possibly more slots...
   ))

(defun spawn-foo (parent-foo &rest initargs)
  (let ((default-initargs (list :name (name parent-foo)
                                :value (value parent-foo)
                                ;; possibly more initargs...
                                )))
    (apply #'make-instance 'foo (append initargs default-initargs))))