One thing you could try, without spending any more, is changing around the amp positions in the room. You also have to remember your playing a strat, he's playing a thinline tele, they are much duller and fatter than strats.
You also have to think about whos playing what, as hunter said, but check when your both playing, can you tell if he stops playing or not?
Me and my bro both play in our band, i play a strat, he plays firebirds and teles, i have a 4x12, he has a 2x12, makes no difference to us, we just make sure they are the right volume together and that everything sounds full when wear playing toghether. You just have to find a nice balance of tone. sit down with the band and just have a little experiment.
joe