As werewolves go, Brid's brother, Sean, is the family bad boy. At least that's what's immediately apparent to Ramon when he meets the wolves outside Douglas's house: "His brown hair was cut in a short, plain style, like he didn't give a damn what it looked like as long as it stayed out of his face" Ramon observes. "He wore jeans and a tank top despite the rainy weather" (24.11). We aren't sure if any forthcoming Broadway revivals of West Side Story are into cross-species casting or not, but he'd sure make one heck of a Jet.
Bran may take after his father in diplomacy and honor, but it's pretty obvious that Sean's out for blood. Or maybe that's just because it's Brid who's in danger. We're told, "Bran might have been tough looking, but it was Sean who sent a shiver up Ramon's spine. He looked way too happy about the prospect of violence" (24.19). Like Douglas, Sean inspires a visceral reaction in people who meet him.
When Sam's in the werewolf hospital near the end of the book, he has the similarly frightening experiencing of not just waking up with Sean in the room, but having him ask if he's the one who "did the no-no cha-cha with my baby sister" (30.7). Oops. Not exactly the way you want to meet your sort-of girlfriend's vengeful older brother, but we suppose after defeating Douglas, Sam doesn't have a lot to be afraid of.