Big Brother Instinct: Bear got his nickname in juvenile detention when he saw three inmates trying to drown Fish. He threw one against the wall, the other two ran away, and we can assume both the Denniston brothers were carefully respected afterwards.
Fish tells Rose this is how he feels about her; he doesn't let himself fall in love with her at first, but still goes to great lengths to protect her.
Dark and Troubled Past: As revealed over the second and third books, Bear and Fish have a whopper: while their mother was dying of cancer in a hospital, she and they converted, enthusiastically, to Catholicism, so the boys started going to St. Catherine's high school; they were nerds and bullied - especially Fish, who was thought to be gay and was sexually taunted by an adult man; Father Raymond, the closest thing they had to a normal dad, died under mysterious circumstances, and they started investigating; Mr. Freet, fearing they would suspect him, planted cocaine in their lockers; when they got out of juvenile detention, Bear discovered his father was having an affair; the other woman moved in, and married their father after their mother had finally died; she resented the boys, especially Bear because he had preached unsuccessfully against the affair; but she was also attracted to Bear, and when he refused to give her the wrong kind of kiss, he and Fish got framed for drug possession AGAIN; the charge didn't stick, but their father turned them out of the house without giving them their inheritance from their mother; so they lived at their friend Stephen Foster's house while still illegally investigating Father Raymond's death. That's excluding what happened to Fish offscreen in The Shadow of the Bear.
Darker and Edgier: Black as Night. Blanche is on the run after being framed for drug possession and grand theft...
As of Rapunzel Let Down, which deals with teen pregnancy, illegal immigration, homelessness, prison, kidnapping, and worse, we have a new winner in this category.
The author states she intended the books to alternate between this and Lighter and Softer, but didn't completely succeed. Black as Night - darker and edgier. Waking Rose - even more dark. The Midnight Dancers - serious, but more gentle and philosophical in tone. Alex O'Donnell and the Forty Cyber Thieves - even the title is lighter and softer; there's a lot more humor, and the action scenes get decidedly cartoony. Rapunzel Let Down - isn't even put in the YA section with the others; it was published as adult fiction.
Defrosting Ice Queen: Fish in "Waking Rose" is a male example. Rachel Durham from "The Midnight Dancers" also qualifies.
Meaningful Name: Rose (has red hair, a fiery spirit, and is named for the fairy tale character Rose Red and Briar Rose); Blanche (means white, is quiet and gentle, and named after both Snow Whites); Brier, their surname, means Rose. So their names mean Rose Red ('rose' is a shade of red) and Rose White (in some variations of the story, Snow White's name is changed to this).
Bear points Blanche's name out to her and jokingly calls her Snow White.
Bear is named for being brawny and protective of his younger brother, Fish, who is named for managing to slip out of bad situations. However, there proper names are Arthur and Benedict (Fish's other nickname is Ben).
Sensitive Guy and Manly Man: Played with with the Denniston brothers. Bear is a burly, serious guy with a fierce temper should you cross him, but he has a deep appreciation for art, poetry, and architecture. Fish is scrawny, geeky, and uses brains over brawn, but he's not a romantic at all like his brother and can come off as harsh because he lacks sensitivity.