Orphaned entities within aggregates are not removed
Consider this example:
An entity Image has a many-to-one or one-to-one relation to an entity Resource.
Image is an aggregate root and is stored in an ImageRepository.
Resource does not have its own repository and thus is a practically member of the Image aggregate.
Now, if an Image object is removed, its Resource object remains in the database and can't accessed through any object or repository anymore.