If a different sperm had fertilised my mother's egg, would I still be me?

My father unleashed millions of sperm into my mother 40+ years ago, and one of them found an egg, dived in, and bingo, I arrived nearly 9 months later. If another one of those sperm had got to the egg first, would I still be me? I know my parents would still have had a child, and my brother and sister a sibling, but where would I be?