Steve Burnside: Steve is a rather complicated and conflicted seventeen year-old. His father worked 
for Umbrella, but after selling information to outside sources, he was discovered by the company and sent to Rockfort Island, the company’s prison. Unfortunately, his mother was killed and Steve, too, was imprisoned. It’s quite obvious he developed resentment towards his father and himself as well. When the outbreak occurs on the island, he separates from his father and goes on fighting through the swarms of zombies and monsters.
Claire Redfield: Claire is a survival of the Raccoon City outbreak, originally visiting the town in search for her brother, Chris. After escaping the city, she receives information on Chris’ location three months later and goes to France, where she raids an Umbrella facility. She is caught during the invasion, and sent to Rockfort Island as a prisoner. After the outbreak, her original capturer, Rodrigo Juan Raval, releases her, telling her she won’t survive anyway. And so, she beings her journey on the island.
Claire & Steve Together: Steve spots Claire walking through the wreckage of the island and mistakes her for a zombie. After surviving the boy’s attempt to shoot her down, Claire reveals herself as a human and Steve is automatically infatuated by her beauty. Of course, his right off the bat flirting makes Claire's first impression rather low. He even goes as far as running off without her, claiming she will just slow him down. Ironically, the next time they meet, Steve is need of some rescuing. Claire saves him from roasting to death in a trap room, but Steve insists on continuing his exploration of the island alone.
Eventually, they decide to stay put together, and end up escaping the island via a plane. However, Alfred Ashford, the head honcho of the island, manipulates the plane into auto-pilot, which forces them on a detour the Antarctic. Yet another Umbrella facility to be explored, the two separate until they discover a proper way out of the building. After Steve avenges his parents and his own suffering by killing Alfred, Claire and him see an optimistic turn of events as they believe once and for all they will be safe.
Alas, their escape is halted by Alfred’s twin sister, Alexia, who just finished waking up from a 15 year cryogenic sleep. She captures both of them, but decides to test her life’s work, the T-Veronica virus, on Steve. Chris Redfield manages to show up to save Claire, and when the siblings are forced to go different paths, the female Redfield discovers Steve locked-up. He quickly transforms into a monster and goes after Claire as prey. At the last minute and with his final grip on humanity, Steve recognizes his friend and after being attacked by one of Alexia’s experiments, transforms back into his human form. Seconds before his demise, Steve declares his love for Claire.
NOTE: Obviously the above is just a quick run-through of the events. For a much more detailed description of the events between the two, go here.