Pearl - Hester's daughter, perhaps the first single parent child in American Literature, does what many children do, temper the behavior of their parent. Pearl's existence forces Hester to bridle her passions in order to keep Pearl. Pearl is portrayed as a witch, a fairy, and a sprite. Hester dresses her to look like a living embodiment of the scarlet letter and a reminder of her past sins.
Governor Bellingham - The governor at the time of Hester's transgression, Bellingham, at one point, wishes to remove Pearl from Hester, but is swayed by Dimmesdale (who has been covertly threatened by Hester immediately prior to speaking (you'll have to read the actual passage in chapter 9 where she all but says you'd better make sure I keep my child or else!)).
Mistress Hibbins - The governor's sister is a witch. Everyone seems to know it but him. She recognizes Dimmesdale for who he is.
The Narrator - Most people don't read the introduction to the book, The Custom House. It's incredibly wordy. It is in the introduction that we meet the narrator who comes across an account of Hester Prynne more than 200 years after the incident and writes a fictional account of her life.