f ( $new_parents_count < $parents_count ) {
				continue;
			}

			$parent_order = 9999; // Set default order.
			foreach ( $parents as $parent ) {
				if ( $parent->parent === 0 && isset( $parent->term_order ) ) {
					$parent_order = $parent->term_order;
				}
			}

			// Check if parent has lowest order.
			if ( $new_parents_count > $parents_count || $parent_order < $term_order ) {
				$term_order   = $parent_order;
				$deepest_term = $term;
			}

			$parents_count = $new_parents_count;
		}

		return $deepest_term->term_id;
	}

	/**
	 * Get a term's parents.
	 *
	 * @param WP_Term $term Term to get the parents for.
	 *
	 * @return WP_Term[] An array of all this term's parents.
	 */
	private function get_term_parents( $term ) {
		$tax     = $term->taxonomy;
		$parents = [];
		while ( (int) $term->parent !== 0 ) {
			$term      = \get_term( $term->parent, $tax );
			$parents[] = $term;
		}

		return $parents;
	}

	/**
	 * Checks if an ancestor is valid to add.
	 *
	 * @param Indexable $ancestor     The ancestor (presumed indexable) to check.
	 * @param int       $indexable_id The indexable id we're adding ancestors for.
	 * @param int[]     $parents      The indexable ids of the parents already added.
	 *
	 * @return boolean
	 */
	private function is_invalid_ancestor( $ancestor, $indexable_id, $parents ) {
		// If the ancestor is not an Indexable, it is invalid by default.
		if ( ! \is_a( $ancestor, 'Yoast\WP\SEO\Models\Indexable' ) ) {
			return true;
		}

		// Don't add ancestors if they're unindexed, already added or the same as the main object.
		if ( $ancestor->post_status === 'unindexed' ) {
			return true;
		}

		$ancestor_id = $this->get_indexable_id( $ancestor );
		if ( \array_key_exists( $ancestor_id, $parents ) ) {
			return true;
		}

		if ( $ancestor_id === $indexable_id ) {
			return true;
		}

		return false;
	}

	/**
	 * Returns the ID for an indexable. Catches situations where the id is null due to errors.
	 *
	 * @param Indexable $indexable The indexable.
	 *
	 * @return string|int A unique ID for the indexable.
	 */
	private function get_indexable_id( Indexable $indexable ) {
		if ( $indexable->id === 0 ) {
			return "{$indexable->object_type}:{$indexable->object_id}";
		}

		return $indexable->id;
	}

	/**
	 * Returns the primary term id of a post.
	 *
	 * @param int    $post_id       The post ID.
	 * @param string $main_taxonomy The main taxonomy.
	 *
	 * @return int The ID of the primary term.
	 */
	private function get_primary_term_id( $post_id, $main_taxonomy ) {
		$primary_term = $this->primary_term_repository->find_by_post_id_and_taxonomy( $post_id, $main_taxonomy, false );

		if ( $primary_term ) {
			return $primary_term->term_id;
		}

		return \get_post_meta( $post_id, WPSEO_Meta::$meta_prefix . 'primary_' . $main_taxonomy, true );
	}
}