It's fascinating to watch Janner’s journey because it doesn't feel like a typical chosen-one arc. In the first book, 'On the Edge of the Dark Sea of Darkness', he’s basically just a responsible but resentful older brother. He shoulders the duty of protecting his brother Kalmar, and you can tell he’s exhausted by it, even jealous of Kalmar’s freedom. That grounding in mundane frustration makes his growth later feel earned.
His biggest shift starts when the title of Throne Warden is revealed. Suddenly, that burden he carried out of obligation is transformed into a sacred duty, but one he initially rejects. He has to move from 'I have to do this' to 'I choose to do this,' and that choice is the core of his maturity. You see it in small moments, like when he stops correcting people about who he is and starts leading, even when he’s terrified. It’ relating to him changes from frustration with his family to a fierce, protective love for the entire community of Anniera.
I think the most poignant part of his growth is how his identity settles. He spends so long grappling with not being the 'special' one, the king, the center of prophecy. His character growth culminates not in becoming the most powerful hero, but in fully, peacefully inhabiting his crucial supporting role. He finds his strength in loyalty and sacrifice, which ends up being the most heroic path of all. The final book, 'The Warden and the Wolf King', really cements this—his strength is in his unwavering heart, not a sword.