I married a twin. When I first met them, I couldn’t tell them apart. Then thet became so differentiated to me that I knew who was who even over the phone.
That said, if Zero had a twin it would have been known about a very long time ago.
I don’t know about that. His history is very controlled and scripted.
Some identical twins are more identical than others. I’ve known several twins that one could learn to differentiate, but I have some cousins who nobody could ever tell apart until they decided to sell fingernails to cosmetics companies. They grew them out very long, and one always had a broken nail or two. Their mom kept track of who had which broken nail.