Looking at the shadows ontheir faces I'd guess a low light to the far right, a second light to the right and slightly higher, and also a low light behind to the left (provides a highlight to her right cheek). His eye looks PhotoShopped, so other parts of the image may also be?
Have you had a look at
Strobist? There is also a good book called "Light: Science and Magic" that is a good read.