One of my favorite things about writing is watching the characters change and grow over the course of the book. When my stories start, neither the hero nor the heroine could form a lifelong bond with someone else, but by the time I near the end, they've changed enough that they can have their Happily Ever After (HEA).
I don't believe that one person can change because of another--not in real life and not in fiction either. I heard someone use this analogy: A person is like a locomotive. You can polish the engine for them, you can load the wood box and even stoke the fire, but the one thing you can't do is move the locomotive. That's completely up to them and they will stand still on the track no matter what you do for them unless and until they want to move down the rails. This is how I approach characters in books, too. The hero and heroine will change, but while they might be a catalyst, they're never the reason why the other changes.
My books are full of action and adventure and usually life-threatening situations. These events are what cause and encourage the change because the characters are forced to face their fears.
With IN THE DARKEST NIGHT, Kel is avoiding dealing with his PTSD, shutting everyone out and pulling back. But then Farran shows up and she needs help, and while he'd like to turn his back on her, he can't quite do it. Besides, when he touches her, his mind seems to calm and he desperately wants peace. He agrees to protect her, only while she does calm his mind at times, he also finds himself in a situation that triggers his flashbacks. Kel doesn't change because of Farran, he changes because his situation has become so intolerable, it's worse to stand still than it is to move forward.
Farran goes through her own growth in the book, but not because of Kel. She was physically abused and knows her magic isn't strong, so she is content to stay in the shadows and let others fight her battles. But the book opens with a scene where there is no one else who can fight for her. She's alone. She has to find the strength and will to battle for herself. And she does. This is the beginning of her change and growth. Not meeting Kel. Even if she never ran into him, she'd have grown into a stronger person because the situation demanded she find her own power. She has a demon and shadow walkers after her, unless she wanted to die, she had to fight and be strong. And she did both.
People never change because of other people, they change because they want to change. And characters, like real life humans, don't particularly like change. Change is scary. So it's my belief that they need to be thrown into a plot where not changing is suddenly worse than doing the work it would take to overcome their issues.
I call this torturing the characters. I love it and they totally deserve it.
