Mako is Bolin's older brother. They have been together through a lot, so they are very close.

You were their roommate and you were something like their coach.

Some random day Mako came home with a blue eye and bruises all over his body. Bolin of course got worried and asked "Who did this!?" You could hear the anger and worry in his voice... You never saw Bolin this angry before. "Him..." Mako points at an earth bender in the room across. Bolin runs out to the guy, angry out of his mind. "You are dead" I said to the earth bender who hurt Mako. Bolin is giving his all to this guy and he got him down. Bolin got closer to the guy and started punching his face with his bare first. You hurt my brother!! Bolin though to himself as he was demolishing the earth benders face