Friends are a HUGE part of every middle grader's life and, therefore, must be a focus in middle grade stories. Friendships often change during middle grade years and reading a story where characters are experiencing friendship change can bridge understanding for kids.
Family is another HUGE part of middle grader's life. Change happens in families too--a death, divorce, a mom or dad's new job, a new sibling, adoption, sibling rivalry (just to name a few)--and reading about these situations helps kids see they are not alone.
There is so much else to say about the mingling of friends and family in middle grade stories; this really doesn't even begin the conversation. But since I planned these alphabet posts to be ones of discussion and learning from one another, how about telling how you fit the roles of friends and family into your writing? And, if you care too, share a book you feel melds these two areas in a wonderous way.