Ok.. maybeeee...
Chef and Sadistic Blondie hooked up. That's why blonde remembers a big D and why Chef was nekkid on the floor with scratches.
Engaged dude (who hates omegas), came back because he secretly likes THIS omega. They did the deed. After her left, gray haired dude went in for a turn.
Buuuut.... gray hair guy said he didn't do anything without a condom, right?
So... conclusion... the baby is Engaged dude's.