Most rebels do keep personal information to themselves, but Erik was already a wanted man before all of this, with a police file and everything. Not knowing his name would be like... not knowing Ted Bundy's name or something. They try to only run the links back to the cell, but a cell leader's name would eventually get out. It seems like Alexi would have to never watch the news, and would have had to decide he wanted that guy basically from looking over Mois' folder and seeing his picture. I can just imagine this conversation.

Alexi: "I want that one. I like his eyes."
Mois: "What?! That guy is the leader of the rebellion around this area. He's a known criminal, and he's committed tons of terrorist acts that killed many people. He's dangerous."
Alexi: "But he's pretty! I want that one!"
Mois: "Seriously, this is -"
Alexi: "No, don't tell me, I want to find out from him!"
Mois facepalmed at his brother's insanity.