I've always wondered about that - I guess Americans with their obsession for genealogy *would* have terms like that and actually use them... I wouldn't know the terminology for those things in Dutch, or whether there's a difference between "second cousin" and "cousin once removed".

Apart from the long asides, though, or perhaps because of them, your conclusion seems rather extreme for your evidence. Of course there are other relevant differences between people than their generation, and no two persons have exactly the same cultural reference points. But that doesn't mean that "the whole concept of generation is a near total fiction".