Tootsie, The twins are goldfish I'm pretty sure. Why so sure? We have this one goldfish who is constantly pregnant (big and round for a while and thin the next day) and when she's ripe I know which GF are boys. My koi's have no interest in any activities besides eating. Everyone else is too new to figure out who's what.
I put the twins, the only survivors of a recent batch, in a glass jar to check them out and recently put them in a pond plant basket within the pond. They really look like GF, no barbels or koi lips. I feed them crushed pellets. They're growing very fast and still dark gray.