User blog comment:Awayorafk/Reaper Logic: What Bioware was TRYING to get across./@comment-4930593-20120425211005/@comment-2086180-20120425223925

ME1: Citadel is central mass relay. ME3: It is home to "starchild" AI, that controls(or leads/governs/something, since reapers are supposedly independent) the reapers.

Good point about the keepers though. I suspect that you're right, with the keepers being the collector-version of the species that made the reapers/"starchild".