My earliest memory is of my third birthday. There was a wall in my kitchen that my brother and I would record our heights on each year on our birthday. I remember my mom marking my height on the wall. When I looked at where the mark was, I noticed that it was above my older brother's mark from his fourth birthday. I then proceeded to make fun of him because at only three years old I was already taller than he had been when he was four. This is probably memorable because it was a birthday and also because my brother used to torment me all the time, so whenever I could do something to torment him it was pretty memorable. My personality and identity are definitely very different than they were then. Back then I was very boyish and would fight with my brother all the time. Now, however, I am much more feminine and I am a very passive person who doesn't really fight with anyone. My brother and I still torment each other a bit, but not to the extent that we used to.
My twin and I would do the same each year! We used to be the same height, but then after our fifth(?) birthday, I would always be the taller one. I guess you could say that I haven't changed because I still take pride in being taller than her (considering she's 2 minutes older than I am, and never let me forget it).