I don't know if i'm missing something, but is it possible to use a prefetch path for retrieving entities that are related to an entity that has already been fetched? This seems like a logical thing to do, but since I cannot find a way to do it I assume there is a reason it is not there.

As far as I know, you can only pass PrefetchPaths to FetchEntity/Collection (or GetMulti) calls. Why are you interested in doing this? Are you using Adapter or SelfServicing? LLBLGen version?

You fetch the whole graph again, but this time you add the entity you already have fetched to a Context object. This will add the entities fetched through the prefetch path to the existing entity.