Coterie is the generic term for any given group of Kindred. Generally, they are united for a purpose, though this purpose can range from “elite strike sent to destabilize a rival city” to “a bunch of people who like to hang out together.” In effect, it’s really just a convention, a shorthand method of describing any given group of vampires who are gathered together and are of different clans. Brood, by comparison, refers specifically to the childer of any given vampire--though how large that group can be, and if it includes the subsequent childer of the brood members, varies quite a bit.
|You want them to have your back, not at your throat.|
The basic books do a pretty good job of describing what a coterie is, and all the various reasons and why a group of Kindred could come together. Being in a band, assembled as an enforcement arm for the Prince, being the local Kindred in a specific area, enjoying each others company, teamed up to take down a common foe--really, it could be any reason. Where I think the “official” line drops the ball, however, is by making PC coteries unique in the world of Vampire, where it seems like most of the rest of the Kindred are united by Clan and blood far more so than by coteries.
This is one of the legacies of 1st ed., and despite my affection for that edition, it’s something that I feel needs to be excised. The idea that the players coterie, consisting as it does of vampires from various Clans, as being unusual and odd works wonders in a game of anarchs vs. elders, where the players are meant to represent a “third way” in creating a new and modern for vampires to live. Outside of that framework, keeping the NPC’s defined by the Clan and status does them a great disservice.
I think it works better to have the NPC’s in the setting also be in inter-Clan coteries, at least for those that make sense. Having political factions = Clan is rather boring, and limiting. Rather, I like to organize them much as I would a PC group, with an emphasis on the history and development of Kindred society within that city. So, for example, the Prince would have a coterie affiliated with him, while the remnants of the previous regime would form another coterie (which might be tentatively allied with a coterie of anarchs). Other city coteries might be a group of ascetics who seek to overcome the Curse of Caine, while another focuses on enjoying and celebrating what they have, regardless of politics or territory. Each of these would contain vampires of different Clans, of course.
I like this for two reasons, besides aesthetics. First off, it makes each faction a bit more dangerous, since the players may or may not know what the members are capable of. Sure, the Prince is a Ventrue, but what if one of his top allies is a Malkavian? Suddenly having the PC Nosferatu brazenly sneak into a meeting becomes far more dangerous. Secondly, it allows the use of Clan and “family” connections to cross faction line. If a player needs to speak with the aesthetics, having a brood mate or an “uncle” that’s a member can give them access that would otherwise be denied.
The other way to have a team of vampires is through the Brood. I've never actually played a game where all the players were members of the same Brood, unless you count Giovanni Chronicles. This is probably because, well, being a Brood means everyone has to be a member of the same Clan, and most players (and I include myself in this) like to play “special snowflakes”--the guys whose abilities are very different from everyone else's. Yet, the Brood concept remains very appealing, if only because it is perhaps the most “organic” way for a group of vampires to associate and ally with each other. The Requiem Chroniclers Guide has some excellent advice for running a game like this, but I think there is one thing I would do differently.
Just let the players pick their clans, and say they’re all part of the same Brood.
I mean, sure, I get it. This violates the “same Clan” idea of the Brood, and it runs smack dab into the world as presented by the rule books. So what? I mean, unless everyone really wants to play Ventrue, what does it harm? You get the advantage of everyone playing “family,” and the players are happy because they all get to have their own special powers, which you can easily justify as “the Dark Gift expresses itself in many ways.” In fact, I might even dump the Caitiff and let anyone pick any three disciplines they want--subject, of course, to Storyteller approval.
I’m not overly concerned with “balance” in a game, particularly since I find the best way to balance a story is by paying attention to your players and giving them “scenarios” rather than plots which allow them to approach situations as they choose to, rather than as “scripted.” As such, the crazy Gangrel who spends his points on Protean, Fortitude and picking up Celerity and Potence isn't anymore “powerful” that the Ventrue who focuses on Presence, Dominate, and picks up Auspex and Obfuscate. If anything, as a Storyteller, that Venture would scare me a helluva lot more than the Gangrel!