Also

Emily Morris - In several branches (sometimes without a surname) she's a friend of Karyn and Jon's when they're a triad instead of a duo. I've used her myself after seeing her in other stories. Whenever Jon has a sister other than Zoe, her name is usually Jill or Jane. She's generally a twin, but not always. They have a dog, Sydney and Nikita are the two known names of the dog that I remember.