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From the Brave series I've seen, they all have different origins. Some alien, some human, some pure machine (some a mix of the three). So it would take a lot of backstory and retcon to have a single Creator for all of them.

Didn't one of the Brave Saga have unnamed cameos from Eldoran?

But hey, if you want to write a fanfic that encompasses all you've mentioned, then go for it. You could even post it in the Creative forum (NOT HERE). No one is saying you can't, they just may not like the idea.