Good luck.
Why are your Top Five your Top Five? Foundational for all of your essays. You have to be specific in communicating why you’re applying to each to have a chance. Especially if you have a sibling at one of them. The other schools will assume you’re inclined to go to SPS.
Good news for you is that each school is very different, so there’s plenty to differentiate them. I can understand St Paul’s for family familiarity and Lawrenceville for proximity, but Hotchkiss, Andover and Brooks aren’t as obvious. Of course you will tell Lawrenceville its because of Harkness, not because its nearby, and you will talk about the perspective you have gained through your brother at SPS.
But again, these schools are very different, and it seems an odd list to me. Look forward to better understanding how you came about it. In the meantime take your SSAT prep seriously, as you don’t want to give them a reason to ding and already solid application.
Outside of that, don’t try to be what you think they want to see. Don’t start a club or non-profit to check an EC box. Authenticity is everything in this process. As is kindness. You can do everything else right, but if they’re not comfortable that you’re kind, you’re chances are zero.
Good luck!