You know I recall my roommate and I when I was in college having a similar discussion with our roommate in college. Then we kept playing and realized we just sucked. Before long it didn't matter what character he brought into the fight with us because we didn't care. We had brought our game to his level. We realized that when we first started playing he could have beaten us with anyone. Maybe your brothers should do the same
However, it probably wouldn't hurt you either to play with other characters. Probably expand your own game a little bit. Kind of the same principal as playing sports. You can play your own position even better once you understand the other ones.