The majority of my characters are white, mainly just because I'm ridiculously white
I've written a couple Carlos Pena oneshots, so I'm guessing I can tuck Latino under my belt. I also write a lot of James Maslow stuff, and he's Jewish (I think that counts as an ethnicity...
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I don't know, I don't really think about race or ethnicity when it comes to characters; they usually just pop in my head as individuals. I don't really sort through my stories and think "wow, there's way too many white people in this fic, so I have to throw in a black character to even it out." It just is what it is.