"Bro-code" sounds fratboyish and stupid. I usually refer to something called loyalty instead.
As for this case, your friend sounds like a dick; not telling you was a disloyal dick move. Asking you what her family likes for their birthdays is asshattery at its finest. He should've been open with it and just left everyone else out of it. If he thought getting it on with this chick would be worth the risk of losing you as a friend, then perhaps he is not a true friend. I mean, he didn't love her or anything, right?
The same goes for friend number 2, if it bothers you I guess.
My GF has a similar story. Her ex is a walking bag of douche: an unfaithful, ungrateful, pesudo-violent ugly asshole. And he is my GF:s former best friend's best friend. It is quite possible that they've had sex.
This idiot caused my GF untold harm, and made her overly cautious toward relationships as well as depressed for several months. A true friend does not make a fuckbuddy out of your asshole ex.
Jaranja said:
Stupid idiots that can't move on.
[HEADING=1] I SPIT ON YOU! [/HEADING]
You wouldn't agree that his friends taking turns with his ex and keeping him in the dark about is cause for a less hostile tone? It's not even about the chick, it's about his friends acting like shit. Now.