Alright, so 'Moonrise' isn't one single famous title, so I gotta clarify which one you mean because I've seen a few. I think you're probably talking about Sarah Crossan's verse novel 'Moonrise'? If that's the one, the key characters orbit around seventeen-year-old Joe.
Joe is the protagonist, visiting his estranged brother, Ed, who's on death row in Texas for a murder he might not have committed. Their aunt Karen is a central figure—she's the one who raised Joe after their mom abandoned them. Their mom, Angela, is a ghost haunting the edges of the story, her absence shaping everything. Then there's Nell, Joe's sort-of girlfriend back home, who provides his emotional anchor. Ed himself, though often seen through Joe's memories and prison visits, is the sun the whole story revolves around.
The book is really about Joe and Ed trying to reconnect as the clock ticks down. The other characters are reflections of the choices their family made.