From Heroes Wiki
|A look at the man, the Senator, and the brother.|
|Nathan was killed at the hand of Sylar, but not before Sylar took all of Nathan's memories. Matt Parkman used to [sic] his powers to erase Sylar's mind and make him think he was Nathan. But in the process, Sylar's consciousness transferred into Matt's head.|
Months later Sylar's consciousness transferred back into his own body and Sylar regained control of his body. Sylar later tracked Peter down for revenge, but Peter had the Haitian's ability, rendering Sylar powerless. After a brutal fight, Sylar shapeshifted into "Nathan".
Peter led "Nathan" to the roof, and pleaded with him to continue fighting Sylar for his life. But "Nathan" knew he couldn't, said his final goodbye to Peter, and jumped off. Peter caught him, but deep down he knew he had to let go of the brother he loved so dearly...
Peter remembers how he let go of "Nathan's" hand, commenting that is was the hardest thing he's ever had to do. He remembers how Nathan would always buy him an "ice cold cherry Popsicle" after his baseball games, because he always wanted him to savor the victory. He thinks about how Nathan showed him how to love his family, and how he could be a real pain in the ass. Always giving him advice and pushing him so hard it hurt and how to live every moment. He thinks about how Nathan was always there to catch him when he fell, and comments that "even in death, you've left your mark".