Think I understand now. It's kinda difficult, but what you need to do is weigh up whether you'd rather be in a relationship with this guy or whether you'd rather keep your long-term friendship with this other guy. The guy you've known for longer of course will be upset, but that's not to say he won't want to be friends anymore [if I've understood this right, sorry if I haven't]. But like I said, it's a question of whether you'd rather have a relationship or a long-term friendship.
If you've already decided to go with the relationship, then, well...just tell him that you love him as a friend, but that's it. I don't think there's much else you can do, just try and break it as gently as possible. Then hope for the best, I guess.
Sorry to hear all of this anyway Chels, hope you're okay x
