Thomasin, I love the figure on the right, but I do feel the lighting of the figure on the left is not as carefully thought-out--but this may be because you are still working on it. Since he(?) is possibly nearer to the light source but slightly behind the woman, I would expect to see an equal amount of light on him, or maybe slightly less intensity of light if you want to push the illusion of his stepping back in space. The neck and torso seem too uniformly dark (especially in contrast to the face which seems suddenly too light) where actually there might be some light hitting the underside of the neck and chin, and the same pattern on the face. But, again, this might be because it is unfinished.
I think it is important that all the figures in a composition are given equal consideration, whether or not you intend for them to be highly detailed or sketchily indicated, or anywhere in-between. Hopefully this is relevant and helpful. I love the lighting and I am rreally looking forward to seeing the finished (

) work.