Erwin is the commander of the legion, he is someone very kind, honest, very cunning and smart, is determined and responsible with his goals 
Levi is the captain of his squad, he is serious, reserved, with a firm character and clear ideas, secretly very empathetic, It is difficult to gain his trust but once he has it he's overprotective. 
They are both in a relationship, they are willing to do anything for the good of humanity, they are strong, loyal and disciplined.