I know this is a strange request and may not make sense but I have been surprised by this product before.
I have a need to reference a children of a child of an item. i.e. I have an Item that has sales order lines as one of its references. There are tasks assigned to one of those sales order lines. The tasks only have references to the sales order lines but I would like to be able to show a list of the tasks under the item. I can add ItemKey to the task but it seems redundant.
I'd strongly recommend showing example code instead of textual descriptions which are hard to follow and likely only make sense to you. If you can lay out your Data structure in code, including what you have and what you would like to get to then what you're trying to achieve may be more understandable. It's easier to ask for people to fill in the blanks, then have them recreate your scenario and have them write the psuedo code example in their heads. Also consider the POV of what your desired answer would be and whether it's clear that's the answer expected from your question. i.e. what answer are you expecting here?
In summary, show what you mean with code instead of trying to describe it and you should make it clear what answer you're expecting.
Also as this isn't ServiceStack related, you'll have a higher probability of it being answered on StackOverflow, but when asking the question there consider showing what you mean with code and having textual descriptions describing that code.