Is it normal that i'm falling for my best friends?

Hi.
I have 2 best friends right now, they are both males. And both of them have girlfriends.
With one of them, let's call him Fred, he is closer to me than the other, who we'll call Ken for now.
Fred is an amazing guy and has been my best friend since elementary school. As we got older, however, I find myself getting way closer to him. We always hang out and do everything together. Lately, I've found myself thinking of him as more than a friend. I get really jealous when I see him with his girlfriend, but oddly enough I don't hate her. She's nice and we are good friends, but I can't stand to see her with Fred. Also, I think Fred kind of likes me too. He is super protective and on more than one occasion he has called me cute or beautiful or perfect. But then when he says that he's like "Did I just say that out loud?" He has also told me that he loves me, and I say the same back to him. But I just never know whether he loves me as a friend or something more, and I'm afraid to ask.
Ken is probably a better friend than Fred, but Fred has more history with me. Ken is super sweet and would do absolutely anything for me. Unlike Fred, he does not show such obvious signs of attraction for me. He is very loyal and faithful to his girlfriend, so I don't want to get in the middle of that. It's just that I find myself fantasizing and even dreaming about him. I don't know what to do, but I think I like him more than Fred.
When I think of being more than anything with Fred it's nice for a while, but then I get kind of disgusted with myself, like "How can we ever do that?" But with Ken I think about that kind of stuff freely, and I don't find it weird.
What should I do?