I'm kind of amused by the "Terrence's band of girlfriends" bit, because, so far as I know, he only has two -- one of which is the aforementioned Rhea. 
Anyway, I can field a little of this. Simply put, the backstory for most of the characters (the BGC ones) mentioned in here has been posted here on the forums in one story or another (or several) over the past... egads, three years. Some of them are only mentioned in passing. Anything under the Riot Force Reports label would be the safest bet, if you're looking. Utena is Sabre, whom I *think* was introduced already but she's not my character and I have the magic all-access backstage pass (since I write some of these folks and offer snarky commentary), so I may be remembering something I've seen which has yet to be finalized and posted.
As for them knowing secret identities... Rhea doesn't have one and one of her doubles is *in* Riot Force; Terrence doesn't have one because, well, Terrence. You'll note they don't mention Gamma (Lisa), because she does kind of maintain a secret ID. Sort of.
So the chain basically goes BGC Expats -> Riot Force -> Scowly Rhea (Onyx Blast) -> Rhea Prime -> Hero Sandwich.
Edit: Fixed Utena's secret identity, sort of. Because even though I've mapped the Sabre's out before, I still forget from time to time.
--sofaspud
--"Listening to your kid is the audio equivalent of a Salvador Dali painting, Spud." --OpMegs
Anyway, I can field a little of this. Simply put, the backstory for most of the characters (the BGC ones) mentioned in here has been posted here on the forums in one story or another (or several) over the past... egads, three years. Some of them are only mentioned in passing. Anything under the Riot Force Reports label would be the safest bet, if you're looking. Utena is Sabre, whom I *think* was introduced already but she's not my character and I have the magic all-access backstage pass (since I write some of these folks and offer snarky commentary), so I may be remembering something I've seen which has yet to be finalized and posted.
As for them knowing secret identities... Rhea doesn't have one and one of her doubles is *in* Riot Force; Terrence doesn't have one because, well, Terrence. You'll note they don't mention Gamma (Lisa), because she does kind of maintain a secret ID. Sort of.
So the chain basically goes BGC Expats -> Riot Force -> Scowly Rhea (Onyx Blast) -> Rhea Prime -> Hero Sandwich.
Edit: Fixed Utena's secret identity, sort of. Because even though I've mapped the Sabre's out before, I still forget from time to time.
--sofaspud
--"Listening to your kid is the audio equivalent of a Salvador Dali painting, Spud." --OpMegs