usually should consider if thier husband or wife would mind you two being together, first.
then, if you plan to tell them, you should find an excuse on why you really didn't love them if they reject you.
like......, "yeah, you're right, it wouldn't have worked anyways....cause i like a pretty/handsome person, and i couldn't stand being with someone like you that is not."
If you felt like you were falling in love with someone, would you tell them, or would you hold back your feelings for fear of rejection?
if im sure im falling in love with someone, i will find the right time and the right moment to tell him or her. tell that person how you really feel deep inside. reject or not don't matter as long you tell what is bother you. if you get reject than you could be friend with him or her and you have to respect their decision, if you love that person of course you want to see them happy and you can't force someone to love you back, sometime they love you back, sometime you love them only one side. love is wonderful things, love is to give and don't want nothing for return. love is so complicated and hard to understand.