It's a very simple natural look, like window light, but there's no way to get the amount of window light one would need to make those images on 20x24" Polaroid at the subject distances he's using, so I'd say he's using a large softbox as the main light, and maybe a reflector for fill. Nothing too complicated.

If you're using a smaller format and maybe not shooting quite so close, you could do it with light from a large window and maybe a sheet of foamcore for fill, if you don't want to invest in a softbox and strobe.