4 Square Portraits in Blue

Here's another round of portraits. Starting on the upper left and going clockwise... An acquaintance from a few years ago, then my old friend Bob, then my old friend Lori. 
Now, can you guess that 4th portrait on the lower left?

I did all these portraits with a Hoh-i-Noor Polychromos dark blue pencil 3800 / #19 on drawing paper.