I am me, right? What if I wasn't completely me? Would I still exist?

[BalancedOne]

Physically, I was once a single sperm and a single egg, right? What if in the race to the egg, the sperm beside the one that created me had won? Would I still be alive today? What is it that makes me who I am? Is this a stupid question? That's the thought that has always confused me about identical twins. They both came from the same egg and sperm, right? So even though they split and became 2 different people, what if they hadn't split? Which one of them would exist? I'm probably going to be roasted for asking such a dumb question. I'm just curiuos about some of your thoughts.