When she was younger, her twin sister Maysilee Donner was selected as a tribute for the Second Quarter Quell, the same Hunger Games that Haymitch Abernathy won. Mrs. Undersee was friends with Mrs. Everdeen when they were children. Maysilee died during the 50th Hunger Games and Mrs. Undersee was never the same afterwards, suffering from massive headaches in her adulthood that caused her to lie in bed all day. Her daughter, Madge, told this to Katniss, and she asked why they didn't get medicines from the Capitol, but was then told that even the mayor had his restrictions. When Gale was whipped, Madge brought some of her mother's medicine to him. In Mockingjay, Katniss finds out that Mrs. Undersee, her husband and Madge, as well as the two people who worked for them, did not survive the bombing of District 12.
Mrs. Undersee's husband is the mayor of District 12. She had one daughter, Madge. Mrs. Undersee also had a twin sister named Maysilee, who was killed in the 50th Hunger Games.
- Mrs. Undersee and Maysilee Donner are the only known pair of twins in the trilogy. Leeg 1 and Leeg 2, despite played by identical twin actresses in the Mockingjay - Part 2 film adaptation, are not explicitly referred to as twins in the book, though it is mentioned they look so similar in uniform that others can't tell them apart.