First, does he know you're gay? If not, start there. The next step may become immediately clear. If he's really your friend, he may be freaked out, but he will deal with it. He may jump ahead of you and say something like "Do you have a thing for me?" If he does, be honest. If he doesn't, you will have to decide if he's ready to hear it from you. After you've told him you love him, he may hug you to his chest and kiss you passionately. That's the fairy tale ending, and the odds are against it. More likely, he'll stand there awkwardly and not know what to say. This is when you say something like, "It's only fair that you know. You're my best friend, and I don't want to lie to you". The ball is now in his court. He may say "thanks, but I'm straight", or he may avoid answering you, and become distant, and the friendship may die. Whatever happens, your relationship will have been changed forever -- that's the risk.
The really tricky thing here is that we all tend to make decisions a little too quickly, when it would be better to just stop and think for a while. Good luck!
just be honest with your feelings or tell your friend first and hear what she has to say
You should tell her about it, as a best friend she should accept your interests in him. In return she may help you win him over.
tell your best friend but tell her not to tell her bro.
To break up with your best friend's brother do this. Talk to the brother about this. Tell him that you are not interested in it anymore.
tell your best friend if they don't mind go for him
It's not best to tell him after a while so be straight and tell him
Imagine him going out with one of your friends. How did this make you feel? Figure out if your feelings are mutual, if not, then tell him you love him like a brother.
Tell your friend thst you like their brother
Tell your boyfriend that they love you then hopefully they will step down a step on the love scale.
Tell his friends in private that you are into someone else. Then tell them that the two of you are close but not in a romantic way. Also tell them that close love is just as good.
Tell him you are not interested in him, and if you were, you would not see him, out of love and loyalty for your best friend.
Tell her "I love you"