Register a page siblings connection in WPGraphQL

wp-graphql-page-siblings-connection.php

add_action( 'graphql_register_types', function() {

	register_graphql_connection( [
		'fromType' => 'Page',
		'toType' => 'Page',
		'connectionTypeName' => 'PageSiblings',
		'fromFieldName' => 'siblings',
		'resolve' => function( $page, $args, $context, $info ) {
			$parent = $page->parentDatabaseId ?? null;

			if ( ! $parent ) {
				return null;
			}

			$resolver = new \WPGraphQL\Data\Connection\PostObjectConnectionResolver( $page, $args, $context, $info );
			$resolver->set_query_arg( 'post_parent', $parent );
			$resolver->set_query_arg( 'post__not_in', $page->databaseId );
			return $resolver->get_connection();
		}
	]);

} );