code: public List<CmsResource> readSiblings(CmsRequestContext context, CmsResource resource, CmsResourceFilter filter)
      throws CmsException {
  
          List<CmsResource> result = null;
          CmsDbContext dbc = m_dbContextFactory.getDbContext(context);
          try {
              result = m_driverManager.readSiblings(dbc, resource, filter);
          } catch (Exception e) {
              dbc.report(null, Messages.get().container(Messages.ERR_READ_SIBLINGS_1, context.getSitePath(resource)), e);
          } finally {
              dbc.clear();
          }
          return result;
      }
docs: Returns a List of all siblings of the specified resource,
  the specified resource being always part of the result set.<p>
  
  @param context the request context
  @param resource the specified resource
  @param filter a filter object
  
  @return a list of <code>{@link CmsResource}</code>s that
  are siblings to the specified resource,
  including the specified resource itself
  
  @throws CmsException if something goes wrong