Hey man I had a listen to the file you sent. Tell your "brothers" to leave audio work to people who know what they're doing. The similiarity is an auditory illusion caused by the voices being overlapped. The two people in the recording you sent me are not the same and don't even sound close. You said they had the same inflections??? No they don't. Those 2 girls are from different regions of the US and even a layman should be able to hear that. There are a few syllables that sound close, but that's the best I could find to support the "theory" that they're the same person.

If that really is the same person, then she's a fucking wicked genious with some damn good equipment. I got 1000s of dollars worth of equipment here and I couldn't make either girl's voice sound like the others. It's especially hard because the 2 girls are using different microphones, and the "anti" has a better mix that's compressed (not good, but still compressed). Your friend (the younger girl) needs to buy a cheap compressor off ebay to stop popping her Ps, or at least get a fucking windscreen for the mic.

I could be wrong though. It's hard to tell with the shitty mix that dude put up. Tell the guy who mixed that to put up some clean samples of each voice and I can give you a 100% answer. Mixing the voices up is a shitty parlor trick that makes them sound way more alike than they are.