Do parallel universes and multiple universes exist?

Could there be another version of you? Yes, this seems impossible. But this is exactly like when Albert Einstein wrote the equation of general relativity. It showed that the world is expanding but he himself said. No, I can't believe it. But 12 years later, observations showed that the universe is expanding. And today, physicists believe that each of us has thousands of possible versions, or in other words, different copies of possible ones in other worlds.