su wanted/off-colour spoilers ahead
so i’m mostly hoping i’m wrong but something about the melded-together gem twins make me think that at least those three fusions (and possibly the sapphire who may be a fusion for all we know!) were experiments that did not prove successful and were stashed away by homeworld who then set out to destroy their creations.
if we consider that the pearl-and-ruby (presumably) fusion consists of two of the most seemingly expendable gems on homeworld we know of so far…that kinda makes sense, in a dark way.
or maybe they were made to fuse together, actually enjoyed each other’s company and ran away because of this??