Hm...is Corazon a Japanese name? It doesn't sound like it.
Unfortunately, I don't know as much about Japanese culture or language as I'd like to, so I don't know what to offer in the way of names. When I came up with Crossfire I pictured him like an Agent Smith character - the sort of guy with aliases and a face that made him blend in. After mentioning you wanted to build on the part-Asian note the name Iho came to mind, but I wasn't particularly thrilled with it. What's Japanese for Hawkeye?
Ordinary names would involve stealing your original John concept. Not that there isn't a hundred everyday names to choose from. I wonder what the most popular Western name is in Japan.
Not all of your characters have to be short, you know. And they're brothers. Even half-brothers would have some similarities. Personality should be opposite, fighting style can be different - hell, he can even be buffer - but there should be something that easily identifies that they're related.
That can be a part of their history, too. Crossfire got his powers from the Fae to help train his brother, since the family refused to without his abilities. They would have gotten even closer when he was alive, but after his "death" those good memories were repressed and the resentment comes out.