Your DS can talk about anything that makes you diverse (not just race/ethnicity) and should not talk about the same thing as your PS (otherwise you're wasting a chance to tall adcomms something different). It also doesn't have to be about overcoming anything. My ds talked about growing up in a high-profile family and how those experiences shaped me. It's best if you can show how you're diverse, based on a story, etc, rather than just say I'm a fob, let me in!