I mean this in a friendly way as possible so please do not be offended,
but it strikes me as a little odd that you have developed feelings, after 5 years, for someone you haven't mentioned as having any particularly attractive qualities.
Do you thinking there is something else going on in your life at the moment, that has lead you to think you have feelings for him that maybe aren't truly romantic feelings? Perhaps you are stressed or lacking in another area of your life at the moment, and he is the most constant and financially/emotionally reliable person you have around you, so you are just feeling warmth and gratitude towards him, and confusing that for romantic feelings.
I may be totally wrong but just a thought.