Maybe more than one of the main cast has a twin-brother somewhere out there. Here are a couple of fictional characters that I think resemble Balthier either in appearance or persona. If you've come over any other look- or act-a-likes for him, feel free to contact me. ^^

If I could choose one person to put in Balthiers cloths for a day, Tsukamoto Takashi would be my pick! The hairstyle he sported as the hot hackerboy in Battle Royale screams Balthier and in my opinion they're the coolest characters in their respective medias. They both display a caring coolness towards those around them.
Both have got the smarts, the will and the skills to accomplish what they want.

It's no secret that FFXII and Star Wars have a few similiarities. A clear and intentional reference is the minor characters Wedge and Biggs who have appeared in many different forms through the FF-series. In FFXII they are emperial soldiers whom you can find outside Nalbina Fortress.
Balthier's counterpart in the Star Wars universe is Han Solo. Both are fast gunmen and fine pilots, with ships of their own. They both have other-raced partners, Fran and Chewie. Solo is a confident man, just like Balthier, and even though they don't share the same profession, bountyhunters are at all four of their heels!
These two free spirits don't want to get involved unless there's something in it for themselves, but in the end they just can't help to do the right thing. They would never leave a friend in need!

This is probably just my current Firefly fandom talking but Malcolm and Balthier seem to have more incommon than just sporting an airship. First of all I'd like to point out that Mal's nickname is Captain Tight Pants, which could very well apply to our favorite Sky Pirate, too.
While Balthier has the Empire to unwillingly fight against, Malcolm has the Alliance. They both take enemies of the government aboard their ships, and letīs these people stay even though it would be much less trouble to just leave them at the nearest harbour.
Malcolm too runs a, mostly, illegal business of cargo transportation and theft. On jobs he partners up with his old warbuddy, the warriorwoman Zoe, who trust him as Fran trust Balthier. Malcolm loves his freedom just as much as Balthier and last but not least they are both sharpshooters with a cocky sense of humour.