The only way to trade gen 3 pokemon from gen 3 games is by using two real life gba hardware and a link cable, although since you're emulating both, it means the save files do exist and can be modified, so you can use a computer to extract the pokemon you wish to give him, and vice versa, and then import them to their respective counterparts, it would've been much better if you both played on emulators on your phones, it's possible to trade there.