When their parents were still alive, it was Mako who was the funny guy and the one who could wear his heart on his sleeves, while Bolin was more aloof, shy, and well-guarded, feeling a little inadequate compared to his firebending brother (at least until he became a man, grew some really large balls, and took on the reins from Lin Beifong as Chief of Republic City). When their parents died, however, they switched roles to cope with their loss and to comfort the other brother. Mako become more aloof and well-guarded while Bolin became the funny guy and the one who wore his heart on his sleeves. As they grew older, both of them would look at one another from time-to-time when the other one wasn’t paying attention, and remember how they were when they were kids, with Mako smiling at the memories he had of those times when he was just like Bolin and how happy he was, and Bolin looking sadly at the same memories, remembering how inferior he felt compared to his older brother and how much he needed to compensate, and hide his pain, by being even funnier.