This is a difficult step to take a friend, it has happened to me more than once that I have a friendship and it ends in a loving confusion. The best you can do is be honest with yourself and your feelings. Nobody deserves to silence what they feel, we all deserve the best version of sincerity, clear accounts keep friendships. I understand that it is easy to say, the problem is to do it. If they are really friends he will understand your feelings towards him and that there is only one friendship and should not bother him, maybe at the beginning if there is much pleasure it will be uncomfortable, but then you will feel much better with yourself and that is what should matter most to you. First your mental health. If they are really friends, he will understand. Nobody breaks the heart on purpose and less when it comes to a friendship.