I think that I have covered everything

I have two tables

Parent Table

Child Table

I established the relationship in the DDT

Established to parentrelationship on the BO

Established the parent BO in the BO on the form.

Configured Childform.

Just checking, but you have set the  Primary and Foreign keys on the Child-Parent Relationship Editor of your Child BO, right?

Also, have you set the ChildBO ParentBusinessObject property on your Child form?

Here is my setup

BO

DDT

Now, is the relationship code executing based off of the parentbo editing state? I have a listview on the parent form which is the child of a parent form.   

1. Open one of the SF samples that shows how to use a relationship (CRM sample application, ChildFormDialog sample, etc).
2. Post a quick sample of your basic implementation on this thread and I will correct your problem (within the basic sample...not your application code) so you can see what you are missing....this is faster than going back and forth.

In a nutshell, my applications has 3 forms and my parent relationship call was not at the highest form.

This is what I had.

Mainform

Contains a datagridview with a mainBO. From the Mainform, I have a childdialog calling the sub Entryform with the mainBO.

Entryform

This form contains the mainBO and childbo.

I had the parentchild relationship established in the Entryform.

ChildEntryform

Contains the childbo

When I moved the childbo up to the Mainform and established the relationship there, all the relationships worked.

Michael