There is a manga where there are 2 couples who are not a destined pair but the couples meet one another who are destined to be. And drama comes.
http://www.mangago.me/read-manga/shounen_no_kyoukai/
not an omegaverse but something similar, red string instead of fated pairs: http://www.mangago.me/read-manga/cut_hogeol/
Also not an omegaverse but red string
http://www.mangago.me/read-manga/kanawanu_koi_no_musubikata/
I have just finished this manga.. first couple is alpha young master x omega butler. The second couple is alpha head butler x beta assistant head butler.
http://www.mangago.me/read-manga/kashikomarimashita_destiny/
The second couple's story is similar with an interesting twist.
Another manga also kinda have similar plot.. again story about two couples. They're both alpha x omega couples but they choose to not be with their destined ones.
http://www.mangago.me/read-manga/shounen_no_kyoukai/

Ok I have this idea for an omegaverse just imagine it’s a Alpha X Alpha couple and than they both meet their destined pair. Would they choose their destined pair over each other or continue being together? Someone pleaseee make this into a manga!