Complex sentence: It's gradually revealed that Thomas is a deeper, more caring person than he wants to reveal--all his vampire brothers have been murdered by their father, and he risks putting Justine in danger if he shows more than passing affection for her.
Split into simpler sentences: It's gradually revealed that Thomas is a deeper, more caring person than he wants to reveal. His flaky attitude turns out to have a purpose--all his vampire brothers have been murdered by their father, and he risks putting Justine in danger if he shows more than passing affection for her.