There have been a couple like that.
One where 2 out of the 3 friends (2 alphas and an omega) started dating but the omega was fated to the other friend so they became a trouple.
Another one where one alpha was in love with another alpha who was in love with an omega and hated the other alpha cuz he pretended to go after the omega. The problematic alpha bit the omega at the same time as the in love alpha so they became a "unwanted" trouple. Also the omega knows about the problematic alpha's feelings but sort of sworn to secrecy.
http://www.mangago.zone/read-manga/immoral_sandwich/
This is one of them (I think) but the other one I'm pretty sure is a one shot that I can't find T_T
I tried. ¯_༼ • ʖ • ༽_/¯ I read too much manga.

i cant be the only one who had a little scenario where i was picturing how would both of them bitw him at the exact same time