You could go for a typical route, such as intra-family adversity (if there is anything, e.g. your mom's neurological disorder). Cultural Heritage is a thought, but you want to go for an essay that is unique. I do not know your family's' situation, but if you have anything that you can consider ''unique'', which belongs almost solely to your family, then go for it. Maybe if you try researching a bit about your own family history? Not just heritage in general, but something very specific and noticeable.
Was one portion of your family located in the midst of a famous historical event (peace marches, Third Reich, or maybe a revolution of some sort). Family history can be unique enough as long as you don't go too outlandish or back far (in other words, if you are distantly related to famous historical figure x).
Maybe something else. Does any previous generation of your family specialize in any particular trade, etc? Who knows; the possibilities are practically endless.
Sorry if that is a bit vague, but there is nothing else I can really pinpoint from what I know (which is nothing XD )