On this video, photographer Daniel Norton from Adorama demonstrates several ways to light and shoot couples (or even small groups of people standing close to each other).
The most basic way is to put your couple (or group) facing the camera. In this case you will want both of them to be on the same plane of focus (if not you might have one of them not sharp enough in the frame). Compared to a traditional one person shoot you should back out your main light source so you will cover both subjects (of course you need to have a powerful enough light source to be able to compensate for that.
This was kind of basic – a more “advanced” way of shooting two people can be by placing one in front of the other with their bodies faced sideways and their head towards the camera (see the example in the video). Norton uses a grid to make sure each subject gets the light but the background doesn’t – you can use two lights – one for each subject. You will need to close down your aperture if you want both subjects to be in focus – but realisticly – in many cases just the front subject will be in full focus so keep this in mind (you can see this in Norton’s image as well).
The final variation shown in this video is where each subject faces in a different direction – here you will need two lights (preferably with a grid so that they don’t spill).
One thing Norton doesn’t talk about in this short video is that each of these looks gives a different take into the relationship of your two subjects – if one is before the other for example he or she might be more important, if they are facing away from each other it might show a conflict or disagreement (although not always of course) and so on. Think about what type of relationship you would like your subjects to project and stand them accordingly.