i can definitely understand why this would be uncomfortable, and dont think youre in the wrong--if youre not happy with it then you have a right to ask it to stop. theyre your ocs, and if the intention was to rip them off, youre allowed to not be okay with that

i actually found their yt channel earlier today (before i saw this) and they mentioned some of these ocs (not specifically the ones based on your ocs, just in general) so considering theyve literally talked about it, i fully believe you