Is it theoretically possible to create two humans by splitting one human in two?
If you split a human early enough (in the first weeks after fertilization), you can get monozygotic twins.

Other than that, you are in the field of science fiction and we cannot safely answer such question on a science website. I am not sure your question will be accepted in its current format but you may try WorldBuilding.SE.

And if you like fantasy novels, I recommend The Cloven Viscount by Italo Calving! You will definitely not learn much about biology in this book though.