GCAT doesn't even HAVE eyes
Exept no, they don't. This was already stated. John made the ectobabies, and sent them through the portals to earth, turning into him, nana, bro, jade, etc.
When he later scratched his session, those SAME EIGHT BABIES went through DIFFERENT portals INSTEAD of the ones they went through before. You've essentually got sixteen babies now, two of everybody. Those that went to pre-scratch earth, and those that went to post-scratch. it doesn't matter that this causes a parodox because EVERYTHING in Sburb is a parodox.
Same with karkat, Kankri and crew couldn't win because they never made themselves, this was openly stated by Doc Scratch. so they scratched, and Karkat made the grubs, that then went through the portals, both to beforus, and to Alternia.