I think I saw a fanon first name for Stiles in a fic somewhere, presumably cobbled together from the extremely brief and cryptic view we get of his school file-folder. Coach calling him "Bolinsky" in that one ep seems to contribute to a notion that his name begins with a B.

I've found it hard to believe, too, that Sheriff Stilinsky willingly calls his own son "Stiles", but they play the family dynamics so heartbreakingly that I'll buy anything they're selling. We don't really know how old Stiles was when his mother dies, do we?

Well, we'll see what the writers give us. Twenty-four whole eps next season!