Well lets see…Peter wasn’t the traitor so would that mean that James and Lily lived? If so then Peter fits just as he was meant to, the same as Remus and Sirius. He’s family. He’s Uncle Pete. He taught Harry how to play Wizards Chess and beat James every time. He would transform and crawl under the couch whenever Harry’s toy rolled underneath and was too far for anyone else to reach. He’s the one Harry can go to with questions about girls because he can’t go to his parents (embarrassing) and Sirius and Remus are obviously no help…until Harry realizes he doesn’t ONLY fancy girls of course…
He relates to Ron a lot when Ron feels like he’s always on the sidelines of his best friend’s spotlight and he assures him that sometimes being the support is more rewarding than being the center of attention.
Being as observant as he always has been, he’s the one who notices that the constant bickering between Ron and Hermione is actually something different. Something he’s used to witnessing since he grew up around Jily and Wolfstar. He’s been betting on them since the day they met. James, Lily, Sirius and Remus owed him 10 galleons each when the two finally became an item.