I don't know her brother, but I have a sister, who I love very, very much.
Fristly, I would not like my sister living with another guy if they were not yet married. Hypocritical yes, but it's the truth. I've done it, and can do it - but I'm a guy.
Secondly:-
He may be an a**hole, I don't know him. But I do know this... I would do EXACTLY the same thing for my sister. It is however interesting to note that he didn't go through cordoncoron in the first place...
I would never go through my sisters BF. Why? he doesn't deserve that until he marries her. So I would go directly to my sister.
Finally, if my sister was moving to a place she didn't know, I would hook her up with my best friend to show her around. Think about it, You want her to get an appartment in a good neighbourhood - you want her to be safe in this new city. If I had a friend there (and since he's a guy, the friend would be a guy) I would hook her up with him - but, and I repeat but, ALL of my friends know that they shouldn't ever think about fvcking my sister. She's OFF LIMITS.
As I say, I don't know this guy, but I think my line of thought would be standard.
Having said that, I have to question C's commitment to his woman.
She has a dream job ans you are not moving with her. This by the way should be a decision made by both of you.
Why are you even living with her if you are not commited enough to move with her (or her stay)?
And further why are you even worried about this. You are not showing commitment to her.
I woudl also say, that her lieing to you about who was on the phone is a huge red flag. I don't buy the 'joking' line of hers. And more than that, why is she talking to him for 45 mins? that seems like a long time.
I think you have handled this very badly.
I think you need to ask yourself whether this woman is somone that you want to forge a relationship with, if it is, then youd better book yourself a flight out with her. Personally, I wouldn't let my woman move to a new city on her own.