Hilary Gail Dearborn (b. 1990) attended the Charmbridge Academy from 2001 to 2008; she is the older sister of Darla and Mary Dearborn. She is "dark-haired and rather pretty." During her time at Charmbridge, she was involved with the Mors Mortis Society, but eventually broke away from the coven.
In the Spring of 2010, Darla told Quick that Hilary had been a member of the Mors Mortis Society until she graduated, and that in early 2009, Hilary "tried to do something, with necromancy" and "went to the Lands Beyond." Later that Spring, Devereaux revealed to Quick that Darla had lied, and that Hilary had merely earned her family's disappointment by eloping with a Muggle-born and "formally unregister[ing] from the Confederation Census, declaring [herself] no longer part of the wizarding world."
In May 2010, she returned to Charmbridge with her parents and youngest sister to talk with Lilith Grimm about Darla's death.
Hilary is the eldest sister of Mary and Darla Dearborn, the daughter of Mildred Seelye and James Dearborn II, the niece of Gideon Dearborn, the granddaughter of Roberta Carling, James Dearborn, Deborah Leiter, and Osric Seelye, the great-granddaughter of Verity Smith and Michael Dearborn, the great-great-granddaughter of Sarah Thorn and Hercules Dearborn, the third-great-granddaughter of Patience Hallowell and Ezra Thorn, and the fourth-great-granddaughter of Hippolyta Black and Absalom Thorn.