If I recall correctly Tolkien does specifically state in several drafts that *all* the small tribe of Vanyar go to Aman. On the other hand though the Vanyar are all golden haired I don't think he says anywhere that all blond Elves are Vanyar, (if you follow that). In other words there's no reason to assume that golden hair didn't occur in other tribes.
P.S. If Thranduil was blond there's a reasonably good chance his son was as well.
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