Elasticsearch version (bin/elasticsearch --version): 5.6.0

Plugins installed: [] N/A

JVM version (java -version): N/A

OS version (uname -a if on a Unix-like system): N/A

Description of the problem including expected versus actual behavior:

https://www.elastic.co/guide/en/elasticsearch/reference/5.6/parent-join.html

This line is hard to parse due to grammar and formatting errors.
For instance the following index two children documents pointing to the same parent 1 with a `routing value equals to the id of the parent: