Drawing faces with just lines is hard. I've studied many who succeed-starting with Durer,
Hans Holbein the Younger
Aubrey Beardsley, well, now that I look at his work, he does what I do--put in lots of texture and pattern so you don't notice that the faces are not all that great.
Mark Summers: This is a portrait of Dr. Seuss.
He won my heart with his illustrations of my edition of Dr. Spock's classic Baby and Child Care. Dr. Spock marched against the war in Viet Nam, saying,
Dr. Spock said, "Trust yourself, you know more than you think you do." that was a big help.
Here's a picture by Hilary in the chapter about when a new baby comes into the family. I think he captures the ambivalence of a big sister--and look at that poor baby brother!