[SalesForce] Custom Report Types missing related Object

Based on some light reverse engineering.

The "standard" report types are created whenever the enable reports option is checked on a custom object, or a master detail relationship to the reportable object is created, EXCEPT if there is a custom report type that includes the same relationships.

To "reset" things, delete any custom report types for the object you're working with, uncheck 'enable reports' on the object, and then recheck. You'll then have "standard" report types that may have been missing before.

And unlike "custom" report types, "standard" report types include all fields for the object by default and hence don't require maintenance when new fields are added.

For some additional discussion see https://success.salesforce.com/answers?id=90630000000D1oTAAS

Note that there are a large number of variations in the order of things, particularly when your considering deployments. The above behavior may not apply in some cases.

You can only have 2 Master Detail relationships to a Custom Object therefore you would either have to change one of the existing M:D relationships to a Lookup or use a Lookup in this case.

Probably the most important question here is which objects does this custom object need to inherit visibility from and do any of the other objects require things like roll up summary of the custom object's fields.