Biff Loman

 
" I know who I am, Kid." Requiem

This is his comment for his brother Happy. The sentence structure is short but affective. He is know certain that he wants to be who he really is. However, seeing his brother blindly following his dad's way, he can't do anything. Biff is trying to warn Happy about the "truth". His brotherhood with Happy must be important, since he said "kid" to Happy. He is talking as if he is a older man watching someone that did the same mistake as him. Since Happy is important to him, he sound sarcastic when he said that. After his father's death, his brother is taking the same road as Willy. Just as much as he cares about Willy, he does too to Happy. Hence Biff is a caring brother to Happy.