Someone for everyone I'd say, they look like they could be anyone's group of friends in anywhere USA (or whatever nation they reside) ? Doesn't look like heterosexual couples because of the arrangement of male, male, female, female. Looks like it was taken at a casual eatery, so not a bar hookup ? I know I'm speculating, maybe even generalizing, but it looks like the guys could be best friends and same with the ladies. Could also be a school related gathering, where each is a student at the same college (study or group project for a course). I don't see brother and sister or even brother-brother, sister-sister relationships, unless step relationship exists ?