Paul

Origins
Paul, who is portrayed by Jonathan Sadowski, is the older brother of Chris (Jesse McCartney). It is assumed that they both grew up together in the United States. Eventually Paul moved to Europe, specifically the Ukraine and has lived there ever since. Earlier in the film, Chris and Paul are having a discussion on the night out in Kiev with Amanda (Devin Kelley) and Natalie (Olivia Taylor Dudley) in which Chris asks if Paul has called their father. He says he hasn't, but needs to. This gives rise to the assumption that Paul may have had a rough patch with his father and may be one of the reasons he moved to Europe.

Personality & Plot Development
Paul is a somewhat careless and high-strung individual. He is always taking the lead in situations and is hard to overpower when it comes to charisma and attitude. In the beginning of the film, it is said that Paul has been living in Kiev, Ukraine for quite a while and is content being there. Chris and Paul are having a conversation near the window, looking out upon Amanda and Natalie when he jokingly asks about starting a romantic interest in the (newly single) Amanda. In response Chris tells him to quit joking around and knock it off. Sometime the next morning after a night partying in Kiev, Paul is late to breakfast with the group. He tells the group about an "extreme tourism" opportunity and convinces the group to reluctantly go.

Later in the film, Paul tries to blame himself about how he is the reason why Chris is always getting hurt. He beats himself up on this constantly while Amanda tries to reassure him that it is not his fault and that Chris needs him to be strong so they can all make it out alive. After many close encounters with the mutants, developing radiation sickness and losing everyone in the group except for Amanda, Chris is killed by what is presumed to be a containment team from the Ukrainian Military after he is told to stop moving forward (in Russian), but does not understand the order and it shot in the chest, mortally wounding him. He later dies next to Amanda.