I'm imagining their first meeting.
All four of them meet in a bar, almost like some dodgy swingers set-up. The girlfriends do all the talking at first. The guys are shy initially, then they open up and bond over their love of Halo (really?! your favorite weapon is the Shot gun too?!), fried food, soft sofas and TV.
Friendship is born, they become inseparable mates, and then the two gf's are free to live happily ever after.
Said local gf is getting pissed off because instead of having one lazy bf lying on the sofa all day, she has got his new "friend" there as well. She's out earning a living and he can't even wash up the breakfast things and pick up the empty beer cans that litter their tastefully furnished hdb. Cue whining ...