I thought it would be interesting to show the progress from the beginning, so I made this animated gif. (Which is my first brush with anything of the sort, so forgive the imperfection.)
I started by blocking in their shapes in olive green. Then I drew rough outlines with chalk and refined their positions, after which I blocked in the initial colors.
I began to pick out the darkest shadows with purple and blue, then activated the background with some transparent layers and strokes. I knew I’d eventually be adding two abstract elements that had symbolism for the recipient.
I focused first on the young girl, whose small features and mischievous expression I knew would be a challenge to capture both accurately and expressively; then I refined the boys’ faces.
I like to take liberties with my portraits. It is more important to me that they look like their human subjects than any specific photograph used as a reference (I work from several when possible). But at this stage I felt that the facial proportions of the brother in the middle were off, and so I made some adjustments, first in chalk:
Then in paint. After making the final adjustments, I was happy to call this portrait complete.