19 (Almost 20)
Kieren Walker (Brother)
Human Volunteer Force (formerly) Roarton Protection Service (currently)
She is 4 years younger than Kieren. After the rising she is part of the HVF and kills many of the undead, but being faced with her brother in his 'untreated state' brings her to her limits and she doesn't shoot him nor Amy and thus they get treated.
She is said to be seen as a 'rough tough bad-ass' but says she isn't because she couldn't kill Kieren even if her life depended on it.
Initially, Jem is quite hostile to the return of her brother Kieren as being part of the HVF and him being a PDS sufferer puts a strain on their relationship.
Dominic Mitchell confirmed Jem's sexuality to be bisexual on his Twitter. [source]
It was confirmed by Mitchell that, had a third season been made, Jem would have had a girlfriend. (This would then help lessen the blow of the 'bury your gays' trope used with the death of her previous girlfriend, Lisa)
Jem's role in the HVF continues even after Kieren's return to Roarton. Still angry and upset by her brother's unprecedented suicide, she struggles to accept him in the undead state he now is. Despite her misgivings, she still goes to extreme measures to protect Kieren, showing that deep down, her love for him is still strong. They begin to mend their broken relationship at the end of the Series 1, when Jem realises that her brother is still the same person as he was before.
Jem returns to school and decides to re-sit her GCSE's. Her relationship with Kieren is much stronger and they have grown considerably close. However, she omits from telling him the isolation and taunts she receives at school (because her brother is a PDS-sufferer) as she doesn't wish to upset him or make him worry.
Jem is a close friend to Gary as the two bonded when working together in the HVF during the Rising, later the two are brought even closer after the death of Henry Lonsdale which reveals their romantic feelings for each other. Although as Gary had forcefully given Kieren Blue Oblivion, the two break up afterwards.