Theory of the Parallel Realities

I have always been fascinated by the theory of parallel realities. Our world would only be one of a myriad of others, all at the same time similar and different. Constants and variables. (Believe it or not, but it's Bioshock Infinite who started my fascination for this theory).
We exist in each reality, but we are different in each of them. I am only one Mathias Poupinais among thousands, just like all of you. For example:
- In this reality I am as I am. In another I can be a woman. In another I am a celebrity. In another, a criminal. In another I am very old. In another I live at a different time (Middle Ages, prehistory, the 1900s, or even in a future that we do not know yet, etc ...). In another I may already be dead, and in another not yet born. The possibilities are limitless.
I think, and this is my opinion, that even if these realities are real or not, our brain is generally conditioned not to be aware of their existence and to protect us from the paradox that it could create in our mind.
This brings me back to another interesting theory: time simply would not exist and all the events (past, present, future ...) would take place exactly at the same time, and the same, without us being aware of it, because again once, our brain would not support the paradox.
I've talked about parallel realities, but there's another theory that joins it: if we die in a reality, among their infinite number, there's bound to be another where we're still alive. So we never die totally. This would be the true form of what is called immortality. 
After all why not? We do not have proof that it exists, but do we have proof that it does not exist?
The universe in which we live is very complex, and perhaps even more than we think.

Mathias, the Killmaster

Fire and Blood \m/