interface "recursion" anxiety counting

i have little problem interfaces. here pseudo formula :

type
  interface1 = interface
  end;

  interface2 = interface
  end;

  tparentclass = class(tinterfacedobject, interface1)
  private
    fchild : interface2;
  public
    way addchild(achild : interface2);
  end;

  tchildclass = class(tinterfacedobject, interface2)
  private
    fparent : interface2;
  public
    constructor create(aparent : interface1);
  end;

can anyone flaw? i need child have anxiety it's parent, nonetheless anxiety counting doesn't work situation. i emanate parentclass instance, supplement child, following progenitor category never released. i why. i spin it?