I will try to explain this the more simple that I can:

I have a ListView that has a BO named PublicationsBO, the ListView has the usual Add, Edit, Delete buttons. I can add and edit records without problem using the ChildFormDialog.

The ChildForm has also a ListView that has ProductsForPublicationsBO, the relationships are setup and configured, I add a record manually and I can view in List and edit that record using another ChildFormDialog.

My problem is that if I add a new record to the ProductsForPublicationsBO the ParentKey field is not added -remains in 0 - so, this record is not realted to any Publication

In this same app, I use relationships, ChildFormDialogs but in all previous cases that dialogs are called from an MaintenanceForm, not from a ListView form - ChildForm. In all of those, the Parentkey is added by SF without problems.

Can you tell me how to add a new child correctly from a ChildForm?

Maybe StrataFlix does this, but I can not follow that sample because almost is done by code, and I'm not so good trying to addapt the ideas there.

Regards 

Everything is possible, just keep trying...