Elves and orcs are the truest descendants of the First People. And while legends tell of outer beings bearing children, most of those ‘of the blood’ are merely the children of unions between humans and these races. The offspring of these couplings are nearly always seen as members of these races.
There are times, however, where the human blood comes out stronger. Or times when the blood from generations pass shows itself in a human child. These occurrences are rare enough that those of mixed-blood do not have a ‘culture’ to call their own.