But how do you want me to try it with your sister at home?

I'm very busy finishing some things that i have to present at work tomorrow when my girlfriend's brother shows up at home. i tell him to have a drink while i finish but he immediately gets bored of waiting. i continue to ignore him until i turn my head and find him with his cock in his hand. i don't know what is wrong with me but it makes me very horny to see him play with her cock and like a curious kitten i want to try it even if my girlfriend is at home. and how delicious it is, i can't stop sucking.