Posy's mother, Hazelle Hawthorne, tried to take care of her, along with her three brothers. When Posy once got very sick with measles, her mother worked overtime to get her well again. Posy eventually recovered.
In Mockingjay, Posy asked if Octavia, a member of Katniss' prep team, was sick, because the pallor of her skin was a light shade of green. At first Octavia seemed saddened about it, but then Posy said Octavia would look pretty no matter what shade of color her skin was. This gave Octavia a fondness for little Posy.
Posy lived with her mother, Hazelle Hawthorne, and her three brothers; Rory, Vick, and Gale. She never met her father, as he died just before she was born. Katniss Everdeen and her family are very much like family to them, due to her close relationship with Gale. During the 74th Hunger Games, the Hawthornes were publicly referred to as Katniss' cousins, to keep them safe from her and Gale's friendship.
- Katniss heard Posy's voice, along with those of her siblings, when the jabberjays mimicked the voices of loved ones being tortured in the Quarter Quell.
- She is one of the youngest characters mentioned by age in the Hunger Games series.
- In The Hunger Games film, Katniss Everdeen says to Gale at the beginning of the movie that they couldn't live out in the woods because she has Primrose Everdeen and Gale has his brothers to look after, though she does not mention his younger sister, Posy.
- Posy's favorite color is said to be bright pink.