You were too harsh, It wasn't his fault, it was his little brother not him, you don't have to blame it on him. Tell him that you're sorry and that you were just angry.
Sometimes I get a little mean when I'm embarrassed. You really shouldn't have took it out on your boyfriend, and you were a little harsh. I would call him and apologize, and Say that you were just embarrassed. He should understand.
Yeah, he didnt do anything wrong - He just wanted you to know he was sorry for his brothers actions by giving you a kiss... That was pretty harsh. You should probably call him or something to appologise!