Adding to Chloe J.’s and Roman B.’s astute answers.
The best essays tell a story. As Roman B. mentioned, you can write about “a small, everyday moment.” Don’t try to capture your whole life. (You can write a memoir later in life!) Focus on one event and weave it into a story that contains:
(1) a hook — A hook is the opening of your essay that engages the reader right away. It places the reader in a specific moment of time, reveals how you process the world, and promises growth.
Compare “when I was 11, my parents got a divorce” to the power of “I remember the knock at my door more clearly than the words ‘we’re getting a divorce.’”
(2) tension/conflict — An engaging story must illustrate an event or idea that challenged your perspective. Think about your favorite books, movies, and TV shows. There is always something that confronts the protagonist: a devastating event, an antagonist, an opportunity for change.
(3) a specific theme — The theme of your essay is the underlying message or truth that results from the conflict, such as loss, courage, or community.
(4) your unique perspective — Your siblings experienced your parents’ divorce in a different way from how you experienced it. You don’t have to mention other people to illustrate your unique perspective. Just relate it. For example, “Family meant safety and connection” for the before, “divorce meant uncertainty and confusion” for the during, and “I see that divorce creates a new definition of family, safety, and connection.”
(5) emotion — You may assume that every 11-year-old experiences deep loss from their parents’ divorce. But some may feel relief or freedom. Don’t assume that the reader knows how you feel about your conflict. Show them how you felts before, during, and after.
Your Common App essays are an opportunity to demonstrate the potential for future growth by highlighting an occasion of past growth.