Are there any examples of commercially-successful Young Adult novels with multiple male protagonists each of whom has their own character arc?
Percy Jackson & the Olympians only has one POV character (Percy), but the second series, Heroes of Olympus, has several male POV characters: Percy, Jason, Leo, and Frank. There's also Annabeth, Piper, and Hazel. Sounds like a lot for only five books, but he does a good job. The first book only focuses on Jason, Piper, and Leo, allowing them each a couple chapters at a time. The second book focuses on Percy, Hazel, and Frank, with the same format as the first. Then they all meet up in book three, each character getting an equal number of chapters from then on. And each character has their own arc. They each have back stories, drama, some kind of love storyline (either with family or a potential partner) and everyone has an arc that grows with the larger plot arc. Great books. You should read them.
But, a POV character and a protagonist character aren't necessarily the same thing. For example, in To Kill a Mockingbird, Scout is the POV character, but Atticus is the Protagonist. A "POV character" is usually called a "Main Character" and will have a character arc which is quite distinct from the overall story's plot, whereas the Protagonist's character arc is quite tightly connected to the overall story's plot. While it should be noted that the same character can be a main character and a protagonist (I call them "heroes" in that case), I don't know if Jason, Leo, and Frank are protagonists in addition to POV characters. Are they? Also, I believe these particular stories are Middle Grade, not Young Adult.
The story wouldn't be able to move forward without all of them. They are part of the Prophecy of Seven, the driving force of the books, and all do their part to stop the Big Bad at the end of the series. So they're all essential to the story arc. Yes, it's considered middle grade, because there is no graphic violence, cursing, or sex. But all of the characters are late teens and the theme is much more YA (trying to find their place in the world, thinking of the future, etc.)
John Flanagan's series's, Rangers Apprentice and BrotherBand. I think these might have what you are after.
Edit: After further review, Percy Jackson & the Olympians (first series, PJ only POV character) is Middle Grade. Heroes of Olympus (the second serious with seven POV characters) is YA. So HoO should fit your criteria.
