J.C. has been in love with her sister's boyfriend for a long time. And when Brady reached for her - she slept him, and like it usually happens in Harlequin land, she got pregnant. She has some issues and insecurities, mostly because her sister was always the prettier, more successful one in the family. It doesn't help that Brady is still in love with Liz, the sister.
Brady had some rough times. First the his fiancée sent him a Dear John letter while he was in Afghanistan, then he was badly injured by a land mine that killed a friend of his. He is suffering from PTSD and is using alcohol to deal with flashbacks and nightmares. He is seriously messed up.
J.C. and Brady are okay characters, but J.C. did put up with a lot of Brady's baggage. And Brady was occasionally an ass. But he had good moments when I almost loved him, until he does something incredibly stupid and hurts J.C. (which happened a couple of times).
But the worst thing in the book was Liz. I hate her. Her attitude toward J.C. and the way she more or less mined Brady and J.C.'s relationship. "How could he love you when he's still in love with me?" - that isn't the exact quote, but the way I understood her stand. And the way J.C. let Liz manipulate her is annoying as well.
Brady, although far from perfect, is the one who really made an impression on me.