personal history you say?

I have to write my personal history for my application to the University of Washington.
God, I'm stumped. What is my personal history? When it really comes down to answering this question in a way that is not only meaningful but representative of who you are it is pretty freaking daunting. There are so many aspects of my life that have shaped the person I am today. My best friends, my sister and brother, my parents and grandparents, the people I never befriended. The interactions with each of them has no doubt shaped the person I am at this juncture in my life. In many ways I think my statement should be intergenerational; I would love to discuss the influence of my great grandparents on their children and on their children's children and on to me. I mean, my values are derived from these people's personal experiences, but is their history my own? Somewhat, but not really. And if I talk about my friends and our relationships am I saying something personal? Not really. This gets back to the crux of my problem, how well do I know myself? The thing is, it is all connected and these histories matter.

So, where to begin?