code: public boolean hasSiblings() {
  
          try {
              return getCms().readResource(getParamResource(), CmsResourceFilter.ALL).getSiblingCount() > 1;
          } catch (CmsException e) {
              LOG.error(e.getLocalizedMessage(getLocale()), e);
              return false;
          }
  
      }
docs: Checks if this resource has siblings.<p>
  
  @return true if this resource has siblings