When Cecil was fourteen, their mother disappeared, forcing Abby to drop out of school and raise him on her own. Cecil describes her as "reserved and controlling", blaming him for having to drop out of school, while Cecil blamed her for not being their mom. They begun to patch up their relationship when their mother returned. Abby was at their mothers side when she died, Cecil was at work.
Though her brother Cecil attempted to stop her wedding during the ceremony itself (accusing Steve Carlsberg of speaking forbidden truths, a charge that is "a mandatory reason to cancel a wedding" in Night Vale), Abby talked him down from his anger and the wedding was allowed to proceed.
Abby and Cecil do not appear to be especially close; Cecil notes in "The Registry of Middle School Crushes" that they have not spoken in some time. (Cecil also notes that he would like this to change) They do, however, seem to be on good terms: Steve states that Abby loves her brother, and Cecil babysat Janice while Steve and Abby were away.
Since Steve Carlsberg is referred to as Janice's step-father, it is likely that Janice is Abby's child from a previous relationship. When her and Steve first got together, he provided both financial support for Janice, and spiritual support for Abby, something previously done by Cecil.
During the scene in the gym in It Devours! Abby is stated to "approach life with a total practicality", and that she would not collapse with the trauma of that moment until later when she was alone in the shower.
- Episode 44 "Cookies": Cecil mentions that Janice's mother is out of town.
- Episode 53 "The September Monologues": While Steve Carlsberg speaks, he says that he loves his wife, she loves her brother, and both he and his wife love their daughter. He later recounts the incidents with Cecil at Steve's wedding.
- Episode 57 "The List": Cecil notes that Janice and her family are among those gathered in Mission Grove Park. He comments that he doesn't like to talk about Janice's family much, but he does tolerate them "in all the requisite familial ways."
- Episode 65 "Voicemail": Steve Carlsberg mentions in a voicemail message left for Cecil that he and Abby are planning a vacation for the two of them, and asks whether Cecil is willing to babysit Janice while they are away. This is the first time Abby is called by name.
- Episode 68 "Faceless Old Women": Cecil mentions that he is reluctant to move away at the moment because his sister and brother-in-law need him to look after Janice during their vacation. He seems more concerned about disappointing his niece than her parents.
- Episode 69 "Fashion Week": Cecil says that he had Janice over "while her parents were taking a romantic long weekend in the kingdom of the Deros, deep within the hollow earth." This kingdom is apparently accessible by ordering any item from the Arby's "market fresh" menu.
- Episode 70B "Review": Cecil notes that Janice, Abby, and Steve Carlsberg were present at the new Old Night Vale Opera House. Janice later says that her mom was the one who told her that Cecil was planning to move away from Night Vale. Later in the episode, Cecil lists Abby among the reasons that he will live in Night Vale, along with Steve and Janice.
- Episode 71 "The Registry of Middle School Crushes": Cecil lists Abby among the players of Janice's heist as "Abby: my sister, whom I have not spoken with in quite a while, but whom I am hoping to speak with more." Cecil describes Abby creating the illusion of an empty hallway in the doorway of the City Council chambers using mirrors and clip lights, though he later reveals that the heist was only a story and that Abby and the other supposed "players" aside from Janice are safe in their homes.
- Episode 78 "Cooking Stuff: Thanksgiving Special": Cecil mentions that his sister and her husband as well as Cecil's niece would be joining Carlos and him for Thanksgiving dinner.
- Episode 80 "A New Sheriff in Town": Cecil says that he will be sharing some eggnog with his "dearest family: Carlos, Abby, Janice... others."
- Episode 85 "The April Monologues": Steve Carlsberg speaks briefly about enjoying quiet evenings with Abby and Janice. He also mentions that Abby had cooked a delicious-looking dinner the day he was visited by Chad Bowinger, and that the two take turns doing so.
- Episode 89 "Who's a Good Boy? Part 1" Hid away in Carlos' lab with Carlos, Steve and Janice during the strangers takeover. While talking to Cecil, Steve notes, "With Abby around, I can't imagine a bad thing that could happen."
- Episode 90 "Who's a Good Boy? Part 2" Along with her family, she held Steve back from becoming a stranger. She tells Janice she is too young to join Tamika's militia.
- Episode 100 "Toast" Steve says him and Abby had been "dating a long time" before he ever met Cecil.
- Episode 107 "The Missing Sky"
- Episode 110 "Matryoshka" Says she believes in Steve's theories, but shows little interest, making Steve believe she only said it to be nice. Rarely got along with Cecil until after their mother died, Cecil spent a great deal of time with her and her daughter because Janice's spina bifida was "costly and terrifying and exhausting". After Abby met Steve, "he took care of Janice, financially, and of Abby, spiritually.". When Janice was young, Cecil provided a lot of emotional and financial support to Abby, saying he was "comforting a sobbing mother" and "spending away his savings on medical care."
- Episode 125 "A Door Ajar Part 2" Hosted The Really Tall One in her home, she notes a "strong odor that seems to be a combination of ozone, copper, and shrimp permeating the house whenever The Really Tall One is asleep. The odor gets stronger the deeper into unconsciousness The Really Tall One gets."
- Episode 149 "The General"
- Episode 153 "The Heist, Part 1" Bought a new house, described as a "larger home, one with a yard for dogs, no stairs and wider doors for Janice's wheelchair, and even Steve's own "man cave" where he can raise bats and cultivate rare crystals."
- Episode 154 "The Heist, Part 2" Was questioned by the secret police during their investigation into her husband and brother in law.
- Episode 155 "The Heist, Part 3"
- Episode 175 "The October Monologues" Listened to Steve's stories, but never shared his enthusiasm for the truth, telling him to "let it lie, let it lie."
- Episode 176 "The Autumn Specter" As children, her and Cecil's mother would dress them up in homemade Halloween costumes and take them around to houses, where they would vaguely threaten neighbors until they gave them candy.
- Episode 181 "C****s" The day their mother left, Cecil says the clouds were "perfect, fluffy things." during their adulthood when she returned the clouds were "gray and low"
- Episode 182 "It Sticks With You" Was taken to the Redwood Remains State Park three or four times a year as a child, where her mother would walk too fast for her and Cecil to keep up. While their mother did what she needed to, her and Cecil would "play hide and seek, and try to catch toads and even had contests to see who could climb the highest". They always found their mother leaving flowers at the base of a tree.
- Episode 208 "Cecil in The Big City" Cecil gave her a snow globe as a memento from his trip.
- "Ghost Stories"
- It Devours!