Xenia is an English half-blood witch, secondborn child of half-blood wizard Ronald Bythesea and half-blood witch, Pippa Bythesea, and younger sister to Lettice Bythesea. Though her parents are divorced, she still enjoys a happy homelife and spends time with both parents. Xenia attends Hogwarts from 2007-2015, and is sorted into Gryffindor. She starts playing Quidditch in her third year, as a beater, and eventually becomes the team captain by her sixth year. Since her third year, she has been dating Baheerah Shafiq in secret.

Xenia's parents are both half-bloods, though despite attending Hogwarts together, they did not meet until they both worked together at the Ministry. Her mother, Pippa, is an auror, and her father, Ronald, worked a rather simple desk job at the Ministry of Magic. They began dating, and had their first daughter Lettice, while they were still unmarried. They married a year later, and had Xenia after two more years. However, after six more years together, they eventually separated. Lettie and Xenia typically lived with their father during the week, but stayed with their mother during weekends, unless she was otherwise occupied with her work as an auror.

Lettie and Xenia both showed signs of magic young, and it was no surprise when they both recieved Hogwarts letters. Lettie was sorted into Hufflepuff, and Xenia, into Gryffindor. Xenia had been interested in Quidditch before Hogwarts, as their father was a fan and often took them (and eventually only Xenia, as Lettie expressed continual disinterested in sports) to see professional matches. Xenia worked hard to make the Quidditch team, and eventually became a beater for her house team, before finally becoming the captain in her seventh year.

In her third year, she approached a girl from Ravenclaw she'd often noticed eating alone--Baheerah Shafiq, and attempted to make friends with her. Although Baheerah was initially disinterested (in anything that wasn't schoolwork or books), they became friends, and eventually, they began dating after Xenia confessed her feelings for her. Although Xenia has come out to her family and Baheerah has even met them, their relationship is a secret at Hogwarts, as Baheerah is afraid of how her parents might react to knowing she's gay, and seeing as how she has so many sisters who also attend Hogwarts, neither of the girls feel the risk is worth taking.