There are 2 types of Parent Field. In this article, we will explain how it works on the example of the field "Neighboorhood" that have parent field "City"

1. Relationships based on already added properties

It is based on backend adding property. When admin adds property via /wp-admin/ to City XXX and Neighboorhood YYY your search form will understand that Neighboorhood YYY is in the City XXX. 

2. Relationships based on manual choice

If this option is selected. Edit Neighboorhood:

2. Edit any of it

3. Choose parent city and update