Some scientists believe that our universe is actually a multiverse and not a single universe. This is the concept of parallel universes. In other words, there may be another copy of you somewhere out there in this universe!
Some theories say that every time we make a decision, a new parallel universe is created in which the opposite of that decision was what happened. This would mean that there are an infinite number of universes in the multiverse and a very very large number of each of us, each living slightly different lives.
We have this concept of infinity (meaning that something goes on for ever and ever, and never ends) which is often used when we think about space.
The problem with infinity is when you apply it to maths and statistics it gives some weird outcomes. So you can say: whats the chances that there is another universe somewhere in the infinity of space – where every single thing happened exactly like it did during the creation of our universe to create another one identical to ours. The chances of that are absolutely tiny, right? there there still is a chance, no matter how small it is. Now in most cases when the chances of something happening are so incredibly tiny, we can pretty much say the chances are zero. But when infinity is involved, even the tiniest chance will eventually happen. It must, because there is an infinite number of chances every possibility will eventually happen.
So if you accept space is infinite and neverending, then you pretty much have to accept there there are not only other universes, but an infinite number of them!