I almost took my bestfriend's little brother's virginity
That can be very serious. Did you think this would upset you friend?
I didn't expect a cold reaction from my bestfriend.
You should not sleep with a friend's sibling without talking to the friend. This could strain your relationship.
Who do you think you are? I don't like you, who are you to tell me what to do?
I'm sorry, but I'm just saying it may not be the best idea to sleep with someone who has close relationships with your friends. How would the both of them feel that you might be destroying their relationship? How about just telling how you feel about him first?