Why do the Mannings sound like they have a Different accent ??

They sound like thier parents because that is who they were around the most. You will talk like the people around you the most. That tells you right there, that they were probably pretty guarded wit thier children and kept them close most of the time. It makes sense. Here are kids of an NFL qb so thier life was in the spotlight alot growing up. Common sense tells you that since they were around thier parents and the other brothers most of the time, that they would all speak the same.