public function getSiblings($unpublished = false)
{
if ($this->siblings === null) {
$list = new Document\Listing();
$list->setUnpublished($unpublished);
// string conversion because parentId could be 0
$list->addConditionParam("parentId = ?", (string) $this->getParentId());
$list->addConditionParam("id != ?", $this->getId());
$list->setOrderKey("index");
$list->setOrder("asc");
$this->siblings = $list->load();
}
return $this->siblings;
}