If your are referring to this from the Designer Commentary, I don't think it applies:
"Q: When the word ‘any’ is used in the criteria for an ability, how many times is that ability applied when the criteria for the ability are fulfilled? For example, if an ability said ‘Add 1 to hit rolls for models that are within 6" of any models with this ability’, would I add 1 to the hit rolls of a model that was within 6" of three models with the ability, or would I add 3 to the hit rolls? A: The word ‘any’ is treated as being synonymous with ‘one or more’. In your example, this means that 1 would be added to the hit rolls, not 3."
I think this would mean that multiple Aspiring Death Bringers using the command ability would not stack. But a single Aspiring Death Bringer using the ability multiple times would stack. I don't know that it makes sense, but I think that's the correct way to interpret it. Especially now with the new magenta errata regarding using a single command ability multiple times.
You shouldn't have to be a linguist to play this game, but alas........