My mother had only one sibling, a sister 6 years older. What if my grandparents hadn't had a second daughter six years after their first child?
I have heard that it is very hard for people to imagine themselves not around after death. But what if I hadn't been born? What if one of my parents had been a different person? I can see that if both of my parents had been somebody other than who they were, ok, no me. That situation is what applies to you right now? You had different parents that I did and you are different from me. But suppose I was still my father's first-born but he had been with some other woman?
I guess I would have the same right hand, the same right shoulder, the same right hemisphere of the brain but the whole left side of me would be different.