Well, I have returned to this subject to add one more thing, apart from the fact that three people in a portrait means getting the likeness of three people. It is actually easier with three than two to get a nice composition. It is always easier to work with odd numbers than even numbers of subjects when trying to get a dynamic composition. So what I do is always start with a thumbnail sketch (or 2 or 3 or more sketches). First, I decide on the number of people - say it's two. Now with two heads, I know I will have two areas of interest. That is hard to balance without getting boring, so I must add a third area of interest to have that odd number I want. So I start with shapes. I arrange my shapes so I have three areas: #1, the area of most importance; #2, the second area of importance; and #3, the third area of importance.
Now in this example, #1 and #2 are the two heads, and they are both close to equal, but one is in a dominant position. The other is in more dramatic lighting, with the shadow side facing the viewer. They balance well, but alone would not work well. The third area, the hands of the lower person, acts as the #3 area of importance, and together they form a triangle.
Now this need not be the hands; it could be a vase of flowers, or a pet on the lap of one of the two, or even just a book or an object of affection or interest to one of the sitters. Also, the hand of the figure in the back is resting on the shoulder of the front person, adding a line for the eye to follow. This is a very fast sketch and a lot of the details would still need to be worked out. But the thing I want to stress is that the composition is not an afterthought based on what I have for reference, but rather the beginning. I then get the reference needed to carry out the composition to a more detailed sketch. From there, to a final sketch, including values. Then start to paint. By the time I pick up a brush or mix color, I know exactly what the painting will be, starting from a composition of simple shapes. Then all you have to worry about is getting the likeness correct for each person, and not about composition.
As you can see by the sketch I included, the beginning thumbnail need not be detailed at all; but before you start to paint, you need to work out the details beyond that thumbnail. Even at the early stage, you are thinking of lighting - where your darks will be in relation to your lights, and how they form lines, direction. You may find in a sketch that the arm or hand is pointing out the side, taking the viewer out away from interest. Better to see that now and change it, than to see it when you are trying to get the likeness of the sitter. Also, having to move a hand and fake it later because you did not get a reference with the hand where you wanted, or in the position you wanted, will frustrate you to no end. It can even make the difference between a success and a failure.
It is all about design. Although I am not a fan of abstract art in and of itself, I do feel that a knowledge of abstract design is of great importance to the realist painter when designing dynamic compositions. If you treat the objects in your painting not as objects, but as abstract shapes of line and value, it can help in designing your compositions. Then arrange your objects (position the people in this case) within that composition.
Composition first, subjects second. And I have not even mentioned color balance that is just one more step. Hey, no one said this art stuff was easy.
