Amazing line of work. I would only keep working on the shapes, try a little variety besides of the circles (which you already do great) . But stunning work!
Very dynamic characters! Well done! I would only work on the heads relationship with the body, they look a lil bit disconected per say. BUt amazing!
Try drawing the woman with different shapes, let's say that the man is a square, so the woman would be the triangle. The man is top notch!
For the woman I would also try to make the lines more organic and flowy, let her move freely.
Great work!
1) Try using shapes that are already 3D, like cubes intead of squares, that will help with the end result. You could use some x-ray pictures to give you more of an idea and study anatomy before drawing the human form.
I hope I could help. :)
