I don't abandon peoples :P And Alexi doesn't know his name because he told hid brother to keep it to himself :P It may sound weird, but, that's how it is :P In the vaguest sense of reality, he heard ABOUT Erik's exploits and a lot of other infos, but when it came to do finding stuff about the vampire himself, Alexi basically looked at a picture and said "I want that one". I would think that most rebels keep personal things about themselves close to the vest, not letting others in on them unless there is complete trust, but that's my own assumption. However you wanna figure it, ALexi refused to hear the name until Erik himself tells him. He wanted to hear it from his lips alone. Mois knows his name, but as we've seen, Mois is a pushover when it comes to his brother's will :P Mois only knows the name however because he's a great investigator :P

Oh, and you said what he said, not what he thought, so what's that last thing he said that you don't agree with?