Any writer trying to create and develop consistently interesting characters would do well to meet Frog and Toad. That is, the characters dreamed up by Arnold Lobel in his series of children’s books.
Yes, you should also carefully study Anna Karenina, but recognize the genius in the 37 or less pages of Lobel’s stories and learn from them too. A child’s attention span will not accomodate leisurely character development. And, a child is wise to overdrawn or clicheed characters (or animals). They are dull. The spry, “glass half-full” Frog and the grumpy, paranoid Toad are subtle,fully drawn and real as can be– you will surely recognize them from your own circle of friends…