Get child where parent id using java api
I had the same problem yesterday. I found out that the parent and child types both need to be in the same index in order for the parent to be visible to the child.
In this example, organization and campaign are different types in different indexes. You will need to create one index with both of these types defined within it. Everything else I believe is good here so let me know if you have any further issues.
I believe (might be wrong) that you should define campaigns as a type within organizations index. also you should set routing to true to make this works.