User blog comment:ChishioKunrin/YouTube comments on the Volume 3 Opening/@comment-5414218-20151016155050/@comment-26882656-20151016160014

Well putting together people with the same colors isn't a new thing in this fandom. (Adam&Ruby, Ruby&Cinder, Cinder&Blake)

They do have a similar medieval europe look to them. And they are both blond with blue(ish) eyes. (or close enough for people to believe)